Arsenal moved eight points clear at the top of the Premier League with a 2-0 win over Tottenham in the north London derby as Chelsea eased the pressure on manager Graham Potter by beating Crystal Palace 1-0 on Sunday.
Newcastle struck late to beat Fulham 1-0 to reclaim third place and keep alive their title aspirations.
But Arsenal will take some stopping if they are to be denied a first league title since Arsene Wenger's "Invincibles" in 2003/04 after a first league win away to Tottenham in nine years.
A dominant first-half display from the visitors did the damage as Hugo Lloris palmed Bukayo Saka's cross into his own net before Martin Odegaard's long-range effort found the bottom corner.
Aaron Ramsdale denied Spurs their customary comeback from two goals down this season after the break with saves from Harry Kane and Ryan Sessegnon.
A fourth home defeat in five league games leaves Tottenham five points adrift of the top four.
- Potter's relief -
Kai Havertz scored the winner for Chelsea with a towering second-half header on the day the Blues announced the signing of Mykhailo Mudryk for a fee that could rise to 100 million euros (£88 million, $108 million).
Chelsea also paid tribute to former player and manager Gianluca Vialli ahead of their first home game since the Italian great died earlier this month aged 58 from pancreatic cancer.
The action on the field was also overshadowed by the official announcement during the first half that Chelsea had completed the signing of Mudryk, taking their spending beyond £400 million in the first season under Todd Boehly's consortium.
There has not been much to show for that investment so far, but Potter's injury-ravaged squad did enough to grind out just a second win in 10 league games.
Havertz made the breakthrough as he rose highest to power home Hakim Ziyech's cross from a well-worked corner on 64 minutes.
"The crowd were great. They recognised the moment we were in, they recognised the young players on the pitch, and they stuck with the guys and got us over the line," said Potter.
Despite a much-needed win, Chelsea remain 10 points off the top four after Newcastle kept their title dreams alive at St James' Park.
- Super sub Isak -
The Magpies were given a huge let-off when Aleksandar Mitrovic saw a second-half penalty ruled out against his former club for a double touch of the ball.
The Serbian slipped as he took the spot-kick and his right-footed effort rebounded off his left foot into the net.
Newcastle took full advantage as club-record signing Alexander Isak came off the bench to head in the winner a minute from time.
Isak has now scored three goals in four Premier League appearances, but his last came back in September due to injury.
"The goal was a special moment," said Newcastle boss Eddie Howe.
"So pleased for Alex. You want to hit the ground running at a new club and he did before the injury. He had to wait and watch the team do well in his absence. He's worked hard. For these moments the work was worth it."
The victory takes Newcastle back above Manchester United into third in the table on goal difference.