Mikel Merino's first-half header proved the difference as Arsenal strengthened their grip on second place in the Premier League with a 1-0 victory over rivals Chelsea.
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Mikel Arteta's side headed into Sunday's derby winless in their last three league matches, but they produced a much-needed response to restore their four-point cushion over third-placed Nottingham Forest.
Makeshift striker Merino backheaded in the 20th-minute opener from Martin Odegaard's corner to reward waves of home pressure, with Chelsea – who were without the injured Cole Palmer – struggling in a one-sided first half.
Enzo Maresca's side did not improve much after the break as Merino almost doubled his tally, and Arsenal's lead, with a second-half volley that forced Robert Sanchez into a fine stop as the hosts ran out comfortable winners.
Arsenal's win leaves them 12 points adrift of runaway leaders Liverpool, while Chelsea remain fourth – just one point clear of fifth-placed Manchester City and two ahead of Newcastle United, who have a game hand.
How the match unfolded
An unconvincing Chelsea defence was repeatedly exposed in the opening stages, with Leandro Trossard and Gabriel Martinelli going close before Declan Rice blazed over after Sanchez scrambled to parry Wesley Fofana's deflected clearance.
Arsenal soon made their dominance pay when Odegaard's right-sided corner found the stooping Merino, whose near-post flick-on looped over Sanchez to open the scoring.

Chelsea offered little at the other end but almost struck in the 37th minute when Marc Cucurella's optimistic volley slipped through David Raya's grasp and trickled narrowly wide of the far post.
An uneventful second half was brought to life on the hour when Sanchez expertly repelled Merino's left-footed volley on the line after a delightful right-wing delivery by Martinelli.

Cucurella remained Chelsea's unlikely attacking threat, though his weak header from substitute Tyrique George's late cross proved little trouble for Raya as Arsenal held on for the win.
Arteta finds much-needed response
Arteta needed a response on Sunday, having seen his side held to draws at high-flying Forest and struggling Manchester United after their disappointing 1-0 home defeat to West Ham United.
Arsenal duly obliged, racing out the blocks as Trossard steered wide, Martinelli curled at Sanchez and Rice skewed over after Jurrien Timber's cross had caused chaos inside the Chelsea box.
Cucurella also survived handball appeals in the build-up to Rice's chance, with the VAR confirming referee Chris Kavanagh's decision that the full-back's arm was in an expected position without any clear or deliberate action towards the ball.
The hosts' set-piece proficiency then proved decisive for Merino's neat opener before Martinelli – this time from the right of the area – fired over when unleashed by chief creator Odegaard.
Arteta's only criticism may have been that Arsenal's margin of victory was not more handsome, with Merino's volley and Odegaard's tame effort from Rice's cutback the closest Arsenal went to a second after the break.
Arsenal will look to pick up where they left off after the international break when they host top-six challengers Fulham – who were 2-0 winners over Tottenham Hotspur on Sunday – on 1 April.
Palmer-less blues for Chelsea
Maresca had already conceded before Sunday's encounter that there was a "quite big" gap between Arsenal and Chelsea, and Palmer's injury-enforced absence only made that difference in quality greater at Emirates Stadium.
Although Palmer has struggled for form in recent weeks, this was the first time since April 2024 that Chelsea started a Premier League match without him – on that occasion, they lost 5-0 at Arsenal.
Chelsea may have been fearing a repeat as Sanchez twice nearly afforded Arsenal an opener; first teeing up Martinelli with a poor pass before dropping Timber's cross to almost set up Trossard.
Pedro Neto, Christopher Nkunku and Jadon Sancho failed to make an impact, though full-back Cucurella almost profited from Raya's questionable handling with Chelsea's first shot on target.
The same theme continued into the second half, with Neto drilling over an ambitious effort before Cucurella managed only Chelsea's second attempt on target with his late downwards header straight at the untested Raya.
The pause for international football will offer Maresca the chance to ponder Sunday's shortfalls before rivals Spurs visit Stamford Bridge for another derby on 3 April.
Club reports
Arsenal report | Chelsea report
What the managers said
Mikel Arteta: "We should have done much more but we are very happy and it was an important game. We played a top opponent and the team played with an unbelievable spirit and now we go to the international break.
"The only thing we can do is try to win our matches. If we do, we are in a better position."
Enzo Maresca: "I think we were in the game until the end. There was not a big difference in the two games between us. Given the injuries, we fought until the end. After the international break, we can have more players back like Nicolas Jackson and Noni Madueke for the final sprint."
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Key facts
After losing two of his first three Premier League home games against Chelsea (W1), Arsenal boss Mikel Arteta has led them to victories in each of the last three – their longest winning run at home to the Blues in the competition since between 2001/02 and 2003/04 (3).
Chelsea are winless in their last seven away games in the Premier League (D2 L5); their longest run without a league victory on the road since October 2022 to February 2023 under Graham Potter (D4 L4).
Since Cole Palmer joined the club, Chelsea have played three domestic away games without him and lost all three, while failing to score a single goal (eight conceded). This was their first league match without Palmer since April 2024, which was also an away defeat to Arsenal (0-5).