The visitors looked certain to climb out of the relegation zone for the first time for almost four months when Mohamed Diame scored a spectacular equaliser eight minutes from time at Stamford Bridge on Saturday.
A draw would have been no more than Wigan deserved after Branislav Ivanovic had put Chelsea ahead from an offside position just after the hour mark.
The visitors were furious and surrounded assistant referee Dave Bryan and referee Mike Jones, to no avail.
Tottenham’s failure to win at Sunderland allowed the Blues – who have had no shortage of luck since Roberto Di Matteo took charge – to close to within three points of them and two of fourth-placed Arsenal, who host Manchester City on Sunday.
Caretaker manager Di Matteo admitted on Friday Chelsea’s season could only be considered a success if they finished inside the top four and won either the Champions League or FA Cup.
The Italian could be forgiven for expecting to land the job full-time were that the case but reports on Saturday that former Stamford Bridge team-mate Didier Deschamps had been sounded out for the role suggest otherwise.
Two straight wins, including at Liverpool, left Wigan on the brink of climbing out of the bottom three.
It looked like that might happen in a disjointed opening 19 minutes by much-changed Chelsea, who finally tested Ali Al-Habsi when Gary Cahill let fly from 30 yards and the goalkeeper tipped over.
Michael Essien was booked for tripping Victor Moses, whose low drive was too close to Petr Cech after Maynor Figueroa tried his luck from fully 45 yards.
The long-range pot-shots continued and Didier Drogba skidded one narrowly wide but Wigan were starting to trouble a Chelsea defence missing John Terry, with Gary Caldwell nodding over a corner.
Both sides had half-hearted penalty appeals but, for the second game in a row, the Blues were doing nothing to worry Champions League semi-final opponents Barcelona.
The home fans were even reduced to chanting about a pigeon that was flying around the stadium.
That was until the 38th minute, when Mata played a one-two with Drogba, cut inside and shot straight at Al-Habsi.
The rebound fell to Drogba but his header was cleared off the line by Figueroa.
The stand-in Chelsea captain was also denied on the stroke of half-time when another good move saw Al-Habsi tip over his bullet header.
Chelsea showed little improvement at the restart, with Florent Malouda booked for felling James McCarthy as Fernando Torres warmed up.
The home fans finally got behind the team and were almost rewarded when Mata’s sublime dinked ball found Drogba, who was again thwarted by Al-Habsi.
An off-balance Sturridge hooked over before the crowd’s calls for Torres were answered when he replaced Malouda just before the hour mark.
Shaun Maloney was cautioned for a clumsy challenge on Ivanovic, who ultimately made him pay from the resulting free-kick with a 62nd-minute opener that should have been disallowed.
Wigan thought they had cleared the danger but Raul Meireles played the ball back in to an offside Ivanovic, who steered it home.
Ivanovic was the Chelsea hero again seconds later when he blocked Franco Di Santo’s shot on the line after a goalmouth scramble.
A frustrated Figueroa was booked for upending Torres, who was twice close to doubling Chelsea’s lead.
Wigan threw on Diame and Ben Watson for James McArthur and Jean Beausejour, the home side soon responding by withdrawing Essien for John Obi Mikel.
Mata blazed a difficult volley over before the visitors played their last card when Conor Sammon came on for Di Santo.
And their changes paid off when they equalised in spectacular fashion with eight minutes remaining, Diame easily drifting past Ryan Bertrand and crashing an unstoppable shot into the corner.
Sammon went close to getting on the end of Moses’ cross before Di Matteo took off Daniel Sturridge for Salomon Kalou, who rifled into the sidenetting from a tight angle.
Caldwell has a chance to snatch it in stoppage-time for Wigan, which Mata did in the 93rd minute when Torres brilliantly volleyed Drogba’s cross against the post and his fellow Spaniard bundled home.
There was still time for Torres to drill another volley at Al-Habsi as Chelsea somehow secured victory.