Welbeck headed in a heart-stopping 95th-minute winner to give Arsenal a last-gasp 2-1 win over leaders Leicester City, while Eriksen struck in the 83rd minute to earn Tottenham a 2-1 victory at Manchester City on his 24th birthday.
The results of a momentous day left surprise pace-setters Leicester just two points clear of Tottenham and Arsenal, while City’s titles hopes took a heavy blow as they were left six points off the pace.
Welbeck was making his comeback after a long lay-off with a knee injury and manager Arsene Wenger said: “Everyone is extremely happy for him because he’s been out for 10 months. That’s an eternity for a player.”
Wenger added: “It was a pivotal moment today because the mathematics meant it could be eight points or it could be two points. That is a great change.”
Leicester took the lead on the stroke of half-time when Jamie Vardy drilled home his 19th goal of the campaign from the penalty spot after he had been felled by Nacho Monreal.
But Danny Simpson’s 54th-minute dismissal after quick-fire yellow cards gave Arsenal the momentum and substitute Theo Walcott equalised 20 minutes from time before Welbeck sent the Emirates Stadium into raptures.
Leicester manager Claudio Ranieri felt that referee Martin Atkinson had been overzealous in dismissing Simpson after the right-back tripped Alexis Sanchez and then dragged back Olivier Giroud.
“They were normal fouls, but not yellow cards,” said the Italian.
“I think the referee was too severe to us for the sending-off. Eleven v 11, I’m sure we win the match.”
The referee also found himself in the spotlight at the Etihad Stadium, where Eriksen’s late goal took Spurs above Arsenal on goal difference and left City four points below them.
Harry Kane put Spurs ahead with a 53rd-minute penalty after referee Mark Clattenburg penalised Raheem Sterling for handball from Danny Rose’s cross, despite the ball seeming to strike his flank.
After Yaya Toure had wobbled the crossbar for City with a free-kick, substitute Kelechi Iheanacho equalised in the 74th minute by slamming Gael Clichy’s cut-back into the roof of the net.
But Eriksen had the final say for Mauricio Pochettino’s side, gathering Erik Lamela’s fine through-ball and steering a shot past Joe Hart to fire Spurs’ hopes of a first league crown since 1961.
– Liverpool rout Villa –
“It was a game that was very important,” Pochettino told the BBC.
“You could feel it was not a normal game and a real test for us. For that we feel very pleased for the players.
“The mentality was good and a perfect performance against a team with a lot of quality players who are top-class. Full credit to my players.”
City manager Manuel Pellegrini protested about Clattenburg’s penalty call.
“This was a shot that hit the back of Sterling and hit his elbow slightly,” he said. “The referee can’t decide the game in that way.
“We responded well, but we needed to get the three points. We are not going to give up, but Leicester and Tottenham are fighting for the title. We need to keep working. The spirit of the team is very good.”
Elsewhere, Daniel Sturridge marked his first league start since early October with the opening goal as Liverpool romped to a 6-0 rout of hapless bottom club Aston Villa at Villa Park.
Dogged by a succession of niggling injuries, the 26-year-old England striker had not started a league match since the 1-1 draw at Everton on October 4 — the last game before Brendan Rodgers was sacked as manager and replaced by Jurgen Klopp.
He headed in Philippe Coutinho’s inviting cross in the 16th minute and further goals from James Milner, Emre Can, Divock Origi, Nathaniel Clyne and Kolo Toure swept Liverpool to the biggest win of Klopp’s tenure.
“It makes a difference having both Philippe Coutinho and Daniel Sturridge on the pitch,” Klopp told Sky Sports.
“You can only play them when they are fit and available. We want the highest quality on the pitch as much as possible. You saw that today.”
While Liverpool climbed to eighth, three points off fifth-place Manchester United in the Europa League berth, sorry Villa were left eight points adrift of safety.
“I feel humiliated,” said crestfallen Villa manager Remi Garde. “I am sorry for the fans who came to Villa Park.”