Fulham's comeback to secure a 2-1 victory over 10-man Arsenal began in the 85th minute with Steve Sidwell's leveller followed by Bobby Zamora's stoppage-time winner.
Arsenal led following Laurent Koscielny's 21st-minute header but was clearly shaken by Johan Djourou's sending off in the 78th.
Earlier in the day, Chelsea appeared set to drop points when Stephen Ward cancelled out Ramires' goal in the 84th minute, but Frank Lampard produced a late goal to secure a 2-1 win.
Chelsea now has a one-point advantage over Arsenal in fourth, but is eight points behind the pace-setters: Manchester rivals City and United.
The focus turns back to the title race on Tuesday night, with City — leaders on goal difference — taking on Liverpool and third-place Tottenham hosting West Bromwich Albion.
For Arsenal just capturing one of the four Champions League places is the priority for a club that used to be a regular Premier League title contender.
Despite an injury crisis in defence, the Gunners had looked like building on its victory over Queens Park Rangers on Saturday when Koscielny headed in his first goal in almost a year at Craven Cottage.
Fulham had squandered several chances to equalize when the game turned in the hosts' favour with Djourou's second yellow card. Having already been booked for catching Sidwell in the 63rd, he went for pulling back Zamora on the edge of the penalty area.
"The first yellow (for Djourou), I felt the referee got all wrong," Arsenal manager Arsene Wenger said.
Compounding Wenger's misery was two former Arsenal players combining to produce the equalizer.
Wojciech Szczesny pushed a corner out to Philippe Senderos, who nodded the ball forward to Sidwell to head home.
And in the second minute of stoppage time, Zamora buried the ball in the bottom corner of the net after Sebastien Squillaci failed to fully clear Stephen Kelly's cross.
"We've been working hard all season and haven't got the home results we want but this caps all our hard work," said Zamora, whose side was routed 5-0 by United two weeks ago. "My ankle and opposite Achilles have been playing up — I've had to have a jab in it to sort it out."
On a frustrating day for Wenger, the pressure eased on his Chelsea counterpart Andre Villas-Boas — thanks to Lampard's late winner.
But the midfielder was fortunate not to have been sent off for a sliding challenge on Wolves winger Adam Hammill midway through the first half.
"My heart was in my mouth over that challenge. I have to admit that," he said. "There was no malice, and I honestly mean that, but I was late and I might have been a bit lucky to stay on the pitch."
Ramires put Chelsea in front in the 54th minute, holding off Stephen Ward's challenge before firing the ball into the roof of the net.
Chelsea's players made a point of celebrating with Villas-Boas, who has endured a mixed first season in charge.
"It's just part of them showing the unity of the team," said Villas-Boas, whose side lost to Aston Villa on Saturday. "This team is focused on getting the consistency in terms of getting the results. If we go on a winning streak of five or six games, which we are capable of, we can be fighting for this league."
In beating Manchester United on Saturday, Blackburn emulated Villa for shock value, but they were brought down to earth by home defeats on Monday.
Blackburn's goal was breached twice in the first half by Peter Crouch as Stoke won 2-1 at Ewood Park. Substitute David Goodwillie pulled one back in the second half, but couldn't prevent Blackburn's third successive home defeat.
Villa was overtaken by Swansea in 11th place after the Welsh club's 2-1 win in the Midlands ended its search for an away success this season.
Nathan Dyer scored after just four minutes and Wayne Routledge added his first goal for Swansea within two minutes of the restart.
Norwich won a battle of promoted sides, coming from behind to beat 10-man QPR 2-1 at Loftus Road.
Captain Joey Barton put QPR in front but later in the first half lost his cool and his place on the pitch with an apparent headbutt on Norwich midfielder Bradley Johnson.
"Hopefully referee sees it retrospectively and sees he's been conned," Barton said on Twitter.
Norwich made its numerical advantage count as Anthony Pilkington equalized with a long-range shot before half time and Steve Morison scored the winner after the break, leaving QPR without a win in eight league matches.