London -Theo Walcott's goal ensured Arsenal overcame Leicester 2-1 and provisionally returned to fourth after withstanding a spirited second-half response by the Premier League's bottom team.
But the victory could have been at a cost with Alexis Sanchez coming off with a knee injury and second-half substitute Aaron Ramsey forced off with a recurrence of hamstring problems.
By that point, though, Arsenal had already scored the goals that ensured it quickly responded to Saturday's derby loss to Tottenham.
Mesut Ozil played a part in both goals, providing the corner for Laurent Koscielny's opener and then seeing Walcott score after his initial shot was parried.
Leicester provided a greater threat after the break, with Croatia striker Andrej Kramaric scoring, but Arsenal held on to take advantage of Tottenham's 3-2 loss at Liverpool. The Gunners went above their London neighbors and Manchester United, which plays Burnley on Wednesday.
"I felt (Saturday's loss) was a bit in their heads, especially in the second half in their legs," Arsenal manager Arsene Wenger said. "We lost our cohesion, our technical superiority, and they were always a danger going forward."
Leicester, to Wenger's bewilderment, remains four points behind Burnley at the foot of the standings.
"When you see the way they are playing football you are surprised they are bottom of the league and that they want to get rid of their manager," Wenger said.
The Frenchman was reacting to uncertainty over the future of Leicester manager Nigel Pearson, who was reported to have been fired on Sunday and the Thai-owned club took several hours to issue a denial.
"They don't want to get rid of me, I'm here," Pearson said when Wenger's comment was put to him.
On the pitch, it was a dominant first-half display from Wenger's side, with Koscielny netting his third goal of the season in the 28th minute.
A fast break forward led to Arsenal's second in the 41st minute before Ozil's shot was parried by goalkeeper Mark Schwarzer and Walcott fired in the loose ball.
Arsenal seemed to have the three points wrapped up, but Leicester's attacking confidence unsettled the hosts.
On the hour, Kramaric's shot was parried by David Ospina and the striker then tried to chip the goalkeeper — only for defender Per Mertesacker to head the ball over from the goal-line.
But from the resulting corner, Kramaric did get his first goal since joining from Croatian club Rijeka last month. Esteban Cambiasso scrambled to retain possession from the corner, the ball reached Riyad Mahrez on the right and his cross eventually reached Kramaric to strike into the net in the 61st minute.
Although Arsenal held on to win, Ramsey limped off less than 10 minutes after coming off the bench and Wenger later bemoaned "a recurrence now of a few muscular injuries" for the midfielder.