A thrilling finish at the Stadium of Light - thanks for following tonight's live commentary and stick around for a full match report, reaction and ratings.
Full-time: Sunderland 2 Chelsea 1. The Black Cats go through to the semi-finals.
Change for Sunderland: Bardsley ON, Giaccherini OFF.
Ki is booked (119) for taking his shirt off in the goal celebration.
Ki Sung-Yeung strikes what is surely the winner! Borini does superbly with his back to the goal after the cross comes in from the right, and feeds the ball left to to the Korean. He doesn't panic, and takes the ball on before scoring low past Schwarzer. 2-1.
GOAL! Sunderland 2 (Ki 118) Chelsea 1
Mannone plucks De Bruyne's right-wing cross out of the air and tries to get Sunderland moving again.
Larsson crosses from the right, Ki heads firmly towards goal but Schwarzer makes a superb save high to his left and stops the shot one-handed for a corner. Celustka stabs the resulting corner wide.
O'Shea does enough to get across Ba to the near post and prevent him turning home Willian's right-wing cross.
Schwarzer has to make two fine saves, first to deny Larsson on the free-kick and then again from Altidore as Ki puts the ball back into the danger zone.
Essien fouls Giaccherini just outside the box on the left and is booked (110). The Ghanaian will be banned against Arsenal on Monday.
After good work by Ba, De Bruyne gets away from O'Shea and tries a shot but it's wide.
Giaccherini releases Altidore, and Cahill tries to clear up but gives away a throw-in.
A dangerous Sunderland corner is cleared by Chelsea. Then De Bruyne wins a free-kick off Larsson.
It seems David Luiz has been for a toilet break, but we're now underway again...
Half-time in extra-time: Sunderland 1 Chelsea 1.
One added minute to be played at the end of the first period of extra-time.
De Bruyne with a cross-shot from the right that's taken cleanly by Mannone. Mikel's taken a knock to the head after tussling with Borini and will need treatment.
De Bruyne tries to work an opening, but the pressure is ended when Essien crosses relatively aimlessly from the right-hand side.
Terrific individual skill from Giaccherini to keep the ball outside the area, the cross comes in from the left from Dossena and Ashley Cole is underneath it - only for Borini to manage to get a shot in after all, but it's wide.
Brown again! Outstanding awareness to intercept Willian's cross ahead of Ba and put the ball out for another corner.
Celustka nutmegs Willian, gets in behind the Brazilian and cuts the ball back, but no Sunderland player is there to apply a finish.
Mannone saves well from David Luiz from the resulting corner.
Brown has largely been excellent in this game, and he's needed again to head clear under pressure from Ba after Willian crossed in from the left.
De Bruyne has the first chance of the additional period, shifting his feet outside the box and firing on his right foot - but it's no threat.
Chelsea get the first half of extra-time underway.
Michael Gray: "Look at the way Sunderland fought, and their determination. The momentum's with them now. Anything can happen." Kevin Phillips: "Eto'o will be rueing that miss, that's been the story of Chelsea's season. Hazard's come on now and he'll be fresh - Sunderland have to go for it."
Full-time in 90 minutes: Sunderland 1 Chelsea 1. Half an hour of extra-time to be played.
After being played through onside, Borini goes down in the box under a tackle from Cahill and wants a penalty. It's not given by Taylor, and replays show the challenge from the Chelsea defender was a good one.
Five minutes of added-on time.
Great strength from Brown to move the ball away from Ba in the box.
Excellent composure by the substitute to fire home from a tight angle after Altidore had kept the ball alive in the box. 1-1.
GOAL! Sunderland 1 (Fabio Borini 88) Chelsea 1
Schwarzer has to punch a Larsson corner clear as Sunderland begin to raise their game in search of a late leveller, and then has to do the same again under pressure from Borini.
Third and final change for Chelsea (83): Hazard ON, Schurrle OFF.
David Luiz is spraying some excellent long-range passes around the Stadium of Light and one of them is sent towards goal by Demba Ba on the volley, but he sends it bouncing across the face and wide.
Mannone is called upon to make a strong save to deny Schurrle, who fired a well-struck shot from the edge of the area.
Schurrle tries his luck again - he wanted a corner for a deflection off Cattermole, but it wasn't spotted by the officials.
Fifteen minutes to go, and there's little to suggest Sunderland are going to find an equaliser here. Meanwhile, Leicester have a goal back through Lloyd Dyer (77) - they now trail Man City 3-1 at the King Power.
Second change for Sunderland (74): Fabio Borini ON, Adam Johnson OFF.
Second change for Chelsea (73): Demba Ba ON, Eto'o OFF.
De Bruyne's ball in from the right is put behind by Brown.
Change for Chelsea (70): Essien ON, Azpilicueta OFF. The Spaniard hasn't been able to run off that knock.
Cattermole gets a shot on goal from long range but it's a comfortable save for Schwarzer. Four of Chelsea's 14 shots have been on target, while only one of Sunderland's eight have been.
Azpilcueta is off the pitch receiving treatment - Sunderland aren't adventurous enough to make the man advantage count.
Pitch invasion at the Stadium of Light - it's a streaker! Stewards taking their time to bring down the offender. Gus Poyet and Jose Mourinho raise a smile.
David Luiz makes a poor clearance straight to Larsson. His shot is blocked by the same Chelsea player, Giaccherini then feeds the ball right to Johnson but his shot is well off target.
Change for Sunderland (63): Ki ON, Gardner OFF.
Still debate raging as to whether the goal should be given to Lampard or not. Regardless, Sunderland need to buck their ideas up if they're going to draw level. Here's a change...
Chelsea's tails are up, and Lampard has a dig from 25 yards but the ball goes over. Goal Decision System replays suggest that the goal should be awarded to Lampard as he touched the ball towards goal, even if Cattermole's boot pushed it on again.
Fine save from Mannone to push away a shot from De Bruyne. Brown heads the resulting corner cleared, and then David Luiz gets the ball back into the danger area but Mannone pounces on it.
The crowd tonight at the Stadium of Light is 20,731.
Chelsea have had 85% possession at the start of the second half. In the other tie tonight, Edin Dzeko has scored again to give Manchester City a 3-0 lead at Leicester.
... and they should have doubled their lead through Eto'o, but he shoots wide of Mannone's left-hand post. That was a poor attempt, after Sunderland had again given the ball away. The Cameroon striker then sees a deflected shot bounce onto the roof of the net.
Chelsea are instantly looking more relaxed after hitting the front...
Such a blow for Sunderland, and many of their fans hadn't yet taken their seats for the second half. But the quality of the ball from Azpilicueta meant that it was just crying out to be stuck away, and Lampard obliged. Looks like it'll go down as a Cattermole own goal, however.
Excellent pass down the right releases Azpilicueta, whose superb low curling cross is perfect for Lampard to run onto. Cattermole tries to block but technology shows the ball is over the line. 0-1.
GOAL! Sunderland 0 Chelsea 1 (Cattermole og 46)
No changes for either side as we restart.
We're about to get underway in the second half. Chelsea will kick us off.
Kevin Phillips: "I'd like to see Sunderland pull the trigger - that's a confidence thing. Chelsea have got lots of firepower on their bench."
Time for a Sky Bet update: Chelsea can now be backed at 10/11 to win in 90 minutes, while Sunderland are still available at 9/2. If you think it'll be a draw (which would mean extra-time), that's 13/8.
Willie Maher on email says: "Jose needs a bit of creativity in the midfield - either switch Willian and Mikel, or take off Mikel and bring on Oscar or Hazard! This game is there for the taking. Still think 2-0 Chelsea though."
Kevin Phillips: "Every time, Chelsea have won the ball back they've created something. They just keep carving out chances." Michael Gray adds: "They get into very good areas, and Sunderland have got away with it on several occasions. Wes Brown keeps giving the ball away."
On the email, it's Brian McCourt: "I don't know what the problem is with the lads but we just can't seem to put the ball into the back of the net. With the likes of Hazard, Oscar and many more, why do we have to be so dependent on our forwards WHO CANT SCORE!?"
Your thoughts at the break? Get your emails into me on firstname.lastname@example.org or tweet me on @jonboy79. Who will be going through to the semis?
Half-time: Sunderland 0 Chelsea 0. Encouraging signs for the hosts, but Chelsea have probably had the better chances overall. A draw about right so far though.
One minute of added-on time.
De Bruyne passes the ball square but it goes straight to Giaccherini, who digs out a shot that goes over.
Cahill to the rescue, with a big clearance after magical dribbling by Adam Johnson had opened up a sight of goal.
Giaccherini finds Dossena again, but his left-wing cross is cleared by Azpilicueta.
Another goal in tonight's other quarter-final tie - it's now Leicester 0 Manchester City 2 (Dzeko 41).
Schurrle collects the ball in midfield and goes on a jinking run towards the area, cutting infield and then shooting - but it's a tame shot and it's well wide.
Azpilicueta robs Brown of the ball and toes it to Eto'o, who tries to manoeuvre himself into a position to shoot only to be bundled off the ball by Brown. No foul given, though, surprisingly.
Willian fires wide after an enterprising move involving Schurrle and Lampard. Replays show the Brazilian's effort took a slight nick off Cattermole. No corner though - we haven't had one yet in the game.
De Bruyne penalised for holding onto Celustka's shorts.
Larsson swings the ball left and Giaccherini plays in Dossena on the overlap. His cross hits Azpilicueta in the arm and there's a huge shout for a penalty, but it's not given by Taylor. The replay suggests the Chelsea right-back did not move his arm to the ball.
Schurrle rather fortunate not to pick up a caution there for hauling back Giaccherini.
For all Chelsea's good early play, it's Sunderland who have had 56% of possession as we reach the half-hour mark. The Blues have had six shots (two on target) to the Cats' two (both blocked).
Another booking, this time for Sunderland (28) - Dossena takes out Willian on the near touchline. No complaints there.
The flag's up for offside against Dossena after a really clever reverse pass on the left from Giaccherini, who's looking the part so far tonight.
David Luiz is the first player booked (25), for obstructing Giaccherini.
Wes Brown clears Azpilicueta's cross from the right as Chelsea threaten once again. Good contest this.
Slightly nervous moments for Chelsea as Johnson crosses from the right and Larsson flicks the ball back for Gardner, but he can't get a clean shot in as the Blues crowd him out.
Eto'o fizzes a low shot at goal from 20 yards but it pinballs off two pairs of legs before the assistant referee manages to raise his flag for offside.
Several Cats players looked offside as the ball was swung in, but the flag was not raised and Azpilicueta had to be alert to make a vital interception before Lampard cleared Chelsea's lines.
Seconds after a wayward shot, David Luiz brings down Adam Johnson and it's another set-piece chance for Sunderland.
Willian played in Schurrle on the right-hand side of the area. Wes Brown slips, and the German fires the ball across the face of goal before Sunderland manage to clear. Another let-off for the hosts, you feel.
Battling play by Cattermole to shepherd the ball out as Schurrle closed in.
Azpilicueta heads way after a cross from the right, following good play by Giaccherini. Altidore needs more support in the Sunderland attack.
Lampard receives the ball in the left channel and has a pop from 25 yards but the shot is no threat to Mannone.
News of a goal in the other quarter-final tie tonight - Leicester 0 Man City 1 (Kolarov 8).
Good play from Giaccherini on the left and he makes an optimistic appeal for a penalty after firing the ball into Cahill's body - not given by referee Anthony Taylor.
Schurrle tried his luck with an ambitious 35-yard free-kick but he got underneath the ball and it flies over Mannone's goal.
Schurrle, De Bruyne and Willian are linking up very effectively in these opening minutes. The latter tricked Dossena and got a goalbound shot away which Mannone had to claim to his right.
Shot from Schurrle saved by Mannone - the German cut in from the left and curled a firm low shot towards goal, but a comfortable save for the Italian.
Chelsea seeing the majority of the ball in the first couple of minutes. Sunderland firmly on the defensive.
Atmosphere sounds good on a cold night on Wearside - Sunderland kick us off.
Price Boosts from Sky Bet - Giaccherini to score first is 20/1; Willian to score first is 9/1; Sunderland to win 2/1 is 18/1; and Chelsea to win 2-0 is 15/2. Teams are out, we'll be underway soon.
Having a bet? Chelsea are 4/7 favourites with Sky Bet to win this tie in 90 minutes; the draw is 100/30 (Burlington Bertie); and Sunderland are 9/2.
Jose Mourinho: "A difficult period is waiting for us. We have to save players. I think these people that didn't play against Palace are in a better condition to play today. What can make the difference is the attitude. They can perform, and we can get the result we need to make the semi-final."
Gus Poyet: "The idea is to become winners. We need to keep growing, play our football, manage the tempo. We've learned a lot from the previous game."
Kevin Phillips, in the Sky Sports studio tonight: "From Sunderland's point of view, the stats don't make good reading. But it's a quarter-final, they've got to try and raise their game." Sunderland haven't beaten Chelsea at home since October 2000 - Phillips scored the winner from the penalty spot.
An ominous stat for you - if you discount penalty shoot-outs, Jose Mourinho has never lost a League Cup tie. 12 of the games Chelsea have played in the competition under him have ended in victories, with the other three drawn.
Matt Hodgson has been in touch on email: "Any team Chelsea put out is technically top class but I do feel they have a tendency to struggle against teams who fight and put them under pressure. I think they'll just have enough quality to go through with a narrow extra-time win, 2-1."
Sunderland, who haven't won in their last five games, haven't reached the last eight of the League Cup since the 2000/1 season, when they were beaten 2-1 at Crystal Palace.
Here's Allan from Cumbria (a Chelsea fan) on email. He's hoping for a big Blues win: "We will get more confidence by keeping the ball, just total dominance. Glad Andre (Schurrle) is playing, another two from him tonight..."
Sunderland and Chelsea have only met once before in the League Cup. It was the 1984-85 semi-finals, and Colin West scored twice to give the Mackems a 2-0 first-leg advantage. They then won 3-2 at Stamford Bridge in the second leg and went through 5-2 on aggregate. However, Norwich beat them 1-0 in the final at Wembley.
Chris Green from Huddersfield has got in touch on email: "Despite being the home team, Sunderland have a challenging evening ahead of them as Chelsea perform well in cup competitions. By all means, anything is possible in football, so I wouldn't completely rule out a shock, but I can't see it happening if Mourinho's men hit the mark."
This is the second time these teams have met at the Stadium of Light in less than a fortnight. Eden Hazard scored two excellent goals on Wearside to give the Blues a 4-3 victory in the Premier League on Wednesday 4 December - but the Belgian is only on the bench tonight.
I want to hear from you tonight, so get your emails into me on email@example.com or tweet me on @jonboy79.
There are eight Chelsea changes tonight, following the 2-1 league win at home to Crystal Palace on Saturday - Mark Schwarzer, Gary Cahill, Ashley Cole, John Obi Mikel, Frank Lampard, Kevin De Bruyne, Andre Schurrle and Samuel Eto'o all start. Branislav Ivanovic is suspended; Michael Essien, John Terry, Eden Hazard and Fernando Torres drop to the bench; Petr Cech, Ramires and Juan Mata are all rested.
Gus Poyet makes three changes to the Sunderland side that drew 0-0 at West Ham in the Premier League on Saturday. Adam Johnson, Craig Gardner and Andrea Dossena come in, while Fabio Borini, Ki Sung-Yeung and Phil Bardsley drop to the bench. Steven Fletcher will not be involved tonight, while Jack Colback misses out again through illness.
Chelsea substitutes: Blackman, Terry, Essien, Oscar, Hazard, Ba, Torres.
Chelsea starting line-up: Schwarzer; Azpilicueta, Cahill, D Luiz, Cole; Mikel, Lampard (captain); De Bruyne, Willian, Schurrle; Eto'o.
Sunderland substitutes: subs: Bardsley, Ki, Cabral, Roberge, Borini, Mavrias, Dixon.
Sunderland starting line-up: Mannone, Celustka, Dossena, O'Shea (captain), Brown, Cattermole, Larsson, Gardner, Johnson, Giaccherini, Altidore.
Welcome to tonight's live interactive commentary on the Capital One Cup quarter-final tie between Sunderland and Chelsea.
Live updates will appear here...