James is beaten to the ball as Gallas heads the winning goal
William Gallas scored a second-half header to earn Arsenal victory in a scrappy match with Portsmouth.
In a drab first half, Portsmouth came close to opening the scoring when Peter Crouch saw his header hit the post.
Arsenal's best opening fell to Emmanuel Adebayor but Sylvain Distin's excellent tackle prevented a certain goal.
After the break, Adebayor and Samir Nasri missed chances before Gallas got in front of David James to nod home the winner from Denilson's cross.
The result lifts Arsenal to fourth place in the table, above Aston Villa, by virtue of having scored one more goal than Martin O'Neill's side, who next play on Tuesday.
Wenger relieved with points against Pompey
But for a long time, it looked as though Arsenal would not get past a much-improved Pompey defence and that visiting boss Tony Adams would get something out of his return to the club he belonged to for 20 years.
In a sluggish opening period, neither side could establish dominance with possession frequently given away cheaply.
Arsenal, lacking creativity in midfield, were finding it difficult to break down a Pompey side that looked intent on eradicating recent defensive errors.
As a result, an uninspiring stalemate ensued - and it was difficult to see who might inject some much-needed pace and inventiveness into the match.
The first real chance came Portsmouth's way and Crouch was unlucky to see his downward header bounce up against the post.
Arsenal responded by creating their only decent chance of the half when Adebayor rounded James and beat Campbell, but he had the ball nicked off his toes by Distin as he was set to score.
The game opened up a little after the break, and Nasri looked as though he could spark some life into the Gunners.
But Portsmouth remained defensively sound, with Papa Bouba Diop, in particular, providing a solid defensive barrier for the visitors.
In keeping with the scruffiness of the match, the scoring opportunities that did arrive were a result of defensive errors rather than attacking brilliance.
Adams prepared for Pompey fight
Twice James got away with failing to deal with a cross as first Mikael Silvestre's header was scrambled clear and, later, Adebayor volleyed into the side netting.
Portsmouth were showing little as an attacking force and Arsenal started to take control as they notched up the pressure.
And it took a decent save by James to prevent Nasri breaking the deadlock, the big keeper blocking with his leg to divert a low shot.
But James will probably feel he should have done better to prevent Arsenal's winner not long after, when Gallas got in front of him to power home a header after the keeper had come out to challenge for a cross.
Arsenal manager Arsene Wenger:
"We were lacking a bit of zip because we gave a lot at Aston Villa in our last match.
"It was important that we were intelligent and patient. Portsmouth played very well and they were well organised and defended very deep.
"My team is maturing quite well, and quickly. We will fight for the title and we believe we have a chance."
Portsmouth boss Tony Adams:
"David James made a great save from a one-on-one, just before Arsenal's goal, that kept us in the game.
"He is a magnificent goalkeeper and I don't have a bad word to say about him.
"I am very proud of my players - they worked their socks off. The players are certainly fighting for me, but we are just not getting the results."
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