Arsenal's Alex Oxlade-Chamberlain, out for five months with a knee injury, scored twice to lead his team to a 2-0 win over Crystal Palace on Sunday and back to the top of the Premier League.
They might only stay there until Monday when Manchester City, who they knocked off the summit, play third-placed Chelsea at the Etihad Stadium, but the 20-year-old Oxlade-Chamerlain's return to fitness should be a huge boost for the Gunners in the title run-in.
Arsenal have 55 points from 24 games, followed by City on 53 from 23 and Chelsea on 50 from 23.
Liverpool, who were held to a 1-1 draw at West Bromwich Albion on Sunday, are fourth with 47 points.
"I've been off the pitch for a while and its great to come back with two goals and help the team to a win," the 20-year-old midfielder told Sky Sports.
Oxlade-Chamberlain, who was injured in the opening match of the season against Aston Villa, has made three substitute appearances in the league as well as starting in the FA Cup against Coventry City before Sunday's return to full Premier League action.
Manager Arsene Wenger decided to play him in the centre of midfield rather than his usual wide position and was rewarded for his decision.
"Crystal Palace were well organised and united in their desire to do the job," Wenger said.
"They are a physically strong side and we knew we had to take advantage of our chances, and we did."
Arsenal needed to be patient to break down a well-organised Palace side who have improved since Tony Pulis became manager at the end of November.
Although they rarely threatened, they defended well until the second minute of the second half when Oxlade-Chamberlain found space at the far post to score with a delicate lob from a Santi Cazorla cross.
Palace went close to an equaliser when Cameron Jerome headed straight at Wojciech Szczesny, but the game was all but over when Oxlade-Chamberlain scored to make it 2-0 after a neat one-two with Olivier Giroud in the 73rd minute.
That was his first goal for Arsenal since December 2012 and his first in any match since scoring for England against Brazil in the Maracana Stadium in June.
Palace remained just one place and one point above the relegation zone.
Earlier, a schoolboy howler by defender Kolo Toure cost Liverpool victory when he gifted West Brom the equaliser in the 1-1 draw at The Hawthorns.
His mistake came after 67 minutes when, under no pressure, he played a loose ball straight across his own 18-metre line to substitute Victor Anichebe standing unmarked on the edge of the box and the former Everton man fired past Simon Mignolet.
Toure could only hold his head in his hands after his dreadful defending which enabled Albion to grab a point from the match Liverpool largely dominated.
"He is an experienced guy so he knows it was a mistake," Liverpool manager Brendan Rodgers told the BBC.
"He is devastated because he is a real conscientious guy. There is no blame for any of them.
"Unfortunately, it has cost us two points but, hopefully, we will see it as a point gained at the end of the season."
Liverpool took the lead in the 24th minute after Raheem Sterling and Luis Suarez linked up on the right of the penalty area with the Uruguayan crossing to the far post where Daniel Sturridge tapped home.
Sturridge has now scored seven goals in his last six successive Liverpool appearances either side of a nine-match injury absence and Sunday's strike was his 50th in the Premier League.
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