The Blues may not be as good as they used to be but even a makeshift line-up was strong enough to put them in touching distance of the Champions League semi-finals.
There was as little to fear from Benfica as Didier Drogba allegedly indicated, the side that helped eliminate Manchester United producing arguably one of the most toothless performances ever witnessed in a quarter-final home leg.
Roberto Di Matteo's gamble of resting six players - including the veterans who inspired the historic last-16 comeback against Napoli - therefore paid off, with Kalou's late winner putting Chelsea on course for a sixth semi-final in nine years.
The fact the Blues look set to finish in the top four in Europe is all the more remarkable considering their are unlikely to do the same in the Premier League.
Di Matteo's selection on Tuesday invoked memories of Andre Villas-Boas' doomed starting XI in the away leg against Napoli but tiredness appeared to be a justification on this occasion.
It also arguably suggested Chelsea's priority lay in ensuring they qualify for next season's Champions League rather than win this year's.
Benfica, though, may have interpreted it as disrespectful, having already taken offence at a perceived slight from Drogba when the quarter-final draw was made.
Surprisingly, the 65,000-capacity Estadio da Luz was far from full, something that was reflected by a strange atmosphere.
The game lacked intensity in the opening 18 minutes but it finally came to life when Raul Meireles was booked for tripping Nicolas Gaitan in full flight.
Moments later, John Terry was caught out by a Bruno Cesar ball over the top but recovered to put off Oscar Cardozo as the striker tried to finish.
Fernando Torres volleyed over wildly after some excellent chest control, before Cardozo nodded Gaitan's pinpoint cross over the top, then Maxi Pereira's ball forced a panicky clearance from David Luiz.
Meireles drilled over from 25 yards before appearing to get away with a handball in the centre-circle.
Benfica were marginally on top but even their slickest moves were leading nowhere, as were Torres' best efforts, another finish sailing over after some neat footwork.
Five minutes before half-time, a goalkeeper was finally called into a meaningful save when Meireles' skidding 25-yarder was palmed wide by Artur.
Luiz was lucky to escape a caution for felling Pablo Aimar moments after the restart but was in the right place at the right time after the free-kick was played in, clearing Cardozo's stinging strike off the line.
Benfica were finally playing with some urgency but their accuracy continued to let them down, as did Kalou's when he wasted a glorious chance for Chelsea, heading over Torres' left-wing cross.
There were handball shouts against Terry when he blocked Pereira's follow-up after Ashley Cole had thrown himself at the initial shot.
Juan Mata could have immediately rubbed salt into the wound by giving Chelsea the lead on the hour mark. Petr Cech's clearance went straight over the Benfica defence to Mata, who rounded Artur but hit the post from a narrow angle.
Axel Witsel's deflected drive almost looped over Cech, who would have been beaten had Jardel's bullet header from Gaitain's cross been either side of him.
Luisao picked up a yellow card for felling Ramires before Di Matteo withdrew Meireles for Lampard, opposite number Jorge Jesus immediately responding by taking off Aimar and Cesar for Rodrigo and Nemanja Matic.
If Benfica were hoping that would be the catalyst for a final push, they were mistaken as Chelsea took the lead 15 minutes from time.
Ramires showed remarkable determination and no little skill down the right to release Torres, who burst into the box and kept his composure to squad for Kalou to slide home.
Ramires hurt himself in the process of creating the chance but was able to continue as Chelsea looked to hold on to a lead away from home in Europe for the first time this season.
Benfica threw on Nolito for Javi Garcia, while Ferreira and Kalou came off for Jose Bosingwa and Daniel Sturridge, whose breakaway should have seen Chelsea kill the game when they wasted a four-on-two chance.
They almost paid in stoppage-time when Cole stabbed Gaitan's cross narrowly wide of his own goal.