Manchester United inflicted Arsenal's first home defeat of the season in a 3-2 thriller to blow the Premier League title race open on Sunday as Aston Villa beat Newcastle to close within four points of the Gunners.
Villa's impressive 2-0 victory at Newcastle took Unai Emery's men level on points with Manchester City, whose own title chances were boosted by events at the Emirates Stadium.
A week on from dominating City in the Manchester derby, Michael Carrick's dream start as United boss continued thanks to Matheus Cunha's stunning later winner.
"A really painful one," said Arsenal boss Mikel Arteta. "But now it is time to be very close to those players that have given us so much joy and support them because we all want to win."
A Lisandro Martinez own goal put Arsenal in front but the Red Devils quickly levelled when Bryan Mbeumo pounced on an error by Martin Zubimendi.
Patrick Dorgu's brilliant strike put the visitors in front early in the second half.
Not for the first time this season, despite their lofty league position, Arsenal were blunt as an attacking force from open play.
But they could rely on their prowess from set-pieces to equalise when Mikel Merino forced in a corner on 84 minutes.
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Just moments later Cunha took aim from outside the box and delivered a telling blow to the Gunners' hopes of a first league title in 22 years.
Victory also propelled United into the top four to boost their chances of Champions League football next season for the first time in three years.
"To come here and score three goals in the manner we did, going one down, coming back, then the setback, and still keeping going," said Carrick. "It was a huge moment for us."
CHELSEA INFLICT MORE PAIN ON PALACE
Villa kept their outside shot at a first league title since 1981 alive with their first victory at St. James' Park for 21 years.
"We are competing against Arsenal, Manchester City, Chelsea, Liverpool, Newcastle, Tottenham... Wow, the power they have!" Emery said. "But we are competing and we are there."
Emiliano Buendia's brilliant strike from outside the box opened the scoring before Ollie Watkins secured victory when the England international headed in Lucas Digne's cross two minutes from time.
Newcastle slip to ninth but still only four points outside the top five, which will likely be enough for a place in the Champions League.
Chelsea piled more pain on Crystal Palace with a 3-1 win at Selhurst Park.
Oliver Glasner promised to do his best to turn around a miserable run for the Eagles despite announcing he will leave the club when his contract expires at the end of the season.
Palace are now winless in 11 games and never recovered after a wayward back-pass from Jaydee Canvot freed Estevao to sprint clear and fire in Chelsea's opener on 34 minutes.
The Brazilian then set up compatriot Joao Pedro to gallop in behind the Palace defence and double the Blues' advantage just after halftime.
Enzo Fernandez's penalty rounded off a fourth win in five games for Liam Rosenior since he took charge at Stamford Bridge.
Nottingham Forest gave their survival chances a huge boost by inflicting just a second home defeat of the season on Brentford.
Forest moved five points clear of the drop zone with a 2-0 win in west London thanks to goals from Igor Jesus and Taiwo Awoniyi.