Pep Guardiola's 49th birthday celebrations went flat as Fernandinho's late own goal forced Manchester City to settle for a 2-2 draw against Crystal Palace, while Chelsea's top-four bid was dented by a surprise 1-0 defeat at Newcastle on Saturday.
On a busy day of top-flight action, the pitchside VAR monitor was used in the Premier League for the first time at Norwich, with Tottenham forced to settle for a goalless stalemate at Watford and Arsenal held to a 1-1 draw by Sheffield United.
It was the drama at the Etihad Stadium that took the spotlight as Fernandinho's last-gasp blunder left Guardiola in no mood to party after City's faint hopes of retaining the title suffered another hammer blow.
The champions trail Liverpool by 13 points ahead of the runaway leaders' clash with rivals Manchester United on Sunday.
"It was a tight game. It's difficult to analyse when they shoot from one corner and have no more chances," Guardiola said.
"We had many chances, unfortunately we could not win."
Cenk Tosun marked his first league start since his loan move from Everton with his maiden goal for the Eagles, the Turkish striker netting a close-range strike from Martin Kelly's flick in the 39th minute.
Sergio Aguero appeared to have turned the game on its head in the 82nd minute when the Argentine striker bagged his 250th goal in 360 games for the club.
Aguero put City ahead in the 87th minute with a typically predatory header from Benjamin Mendy's cross.
But there was a sting in the tale for Guardiola as Fernandinho turned Zaha's cross into his own net in the 90th minute to end second-placed City's run of three successive league wins.
- Chelsea downed late on -
Chelsea would have cemented their grip on fourth place with a win on Tyneside, but they were unable to muster the cutting edge required to break down stubborn Newcastle and fell to Isaac Hayden's header with just 20 seconds left in stoppage-time, losing 1-0.
Chelsea's first defeat in four league matches leaves them five points clear of fifth-placed Manchester United.
After four league games without a victory, this was a much-needed success for Newcastle, but a wasted opportunity for Chelsea to open up a bigger gap in the race to qualify for the Champions League.
"We can't work anymore in training on finishing. You need to have that killer instinct in front of goal. We need to score more goals from front-line areas if we are going to get to where we want to be," Lampard said.
"It's quite clear from what I am saying now that we know where we need to strengthen but we shall see."
At Vicarage Road, Troy Deeney's 70th-minute spot-kick was saved by Paulo Gazzaniga before Tottenham's Erik Lamela was denied a last-gasp winner by Ignacio Pussetto's goal-line clearance.
With England captain Harry Kane sidelined after hamstring surgery, Tottenham have gone three league games without scoring.
Jose Mourinho's side are without a win in four league matches since December 26 and sit eight points behind Chelsea.
Toothless Tottenham thought they had stolen the points in stoppage-time when Lamela flicked Serge Aurier's cross towards goal, but Watford's new signing Pussetto cleared off the line, with goal-line technology showing just 10.04mm of the ball had not gone over.
Arsenal are 10 points adrift of the top four after the Blades continued their superb first season back in the Premier League.
Gabriel Martinelli, 18, broke the deadlock in first-half stoppage-time at the Emirates Stadium with a clinical finish from Bukayo Saka's cross.
But Chris Wilder's side snatched an 83rd-minute equaliser when John Fleck lashed home after Arsenal failed to clear.
Bottom of the table Norwich's vital 1-0 win over fellow strugglers Bournemouth saw the pitchside monitor finally used to decide a red card call.
Norwich took the lead when Bournemouth defender Steve Cook was sent off after flinging himself across the goal to block Teemu Pukki's shot with his hand.
Pukki fired home the resulting penalty in the 33rd minute, but the Canaries had to survive a tense finish after Ben Godfrey was sent off in the 76th minute.
Godfrey's foul on Callum Wilson was ruled a red card by referee Paul Tierney after he checked with the monitor, a move that followed advice to officials from Premier League chiefs this week to use the screen more often.
Wolves climbed to sixth after a 3-2 win at Southampton, Everton drew 1-1 at West Ham and Brighton shared a 1-1 draw with Aston Villa.
Manchester City were held to a draw by Crystal Palace
Hayden's 94th-minute header condemned Chelsea to defeat
Spurs needed a second-half penalty save from Gazzaniga to take a point against Watford