Mikel Arteta scored a penalty and was then sent off as 10-man Arsenal battled to a 2-0 win over managerless Crystal Palace to stay clear at the top of the Premier League.
The Arsenal captain slotted home from the spot at the start of the second half after Serge Gnarby had been upended by Adlene Guedioura.
However, the Spanish midfielder was then shown a straight red card when referee Chris Foy deemed he had prevented a clear goalscoring opportunity when he tangled with former Arsenal striker Marouane Chamakh some 35 yards out.
Palace, who parted company with Ian Holloway following the 4-1 home defeat by Fulham, had Keith Millen in caretaker charge.
They rallied when Joel Ward saw his shot tipped against the bar by Wojciech Szczesny, who then produced a wonder-save to deny Mile Jedinak from the corner.
Arsenal, though, secured all three points when Olivier Giroud headed in with three minutes left after a break by Aaron Ramsey down the left.
Gunners boss Arsene Wenger had opted to start with England midfielder Jack Wilshere, who had been troubled by an ankle problem, on the bench.
Mathieu Flamini, though, returned to the side after missing the midweek Champions League defeat to Borussia Dortmund as a precaution following concussion.
Crystal Palace caretaker manager Keith Millen brought in centre-back Danny Gabbidon as one of six changes. Kagisho Dikgacoi, Barry Bannan, Jerome Thomas, and Guedioura all came in, while Morocco forward Chamakh led the Eagles attack against his old club.
There was a positive start by Arsenal, with Giroud heading over a cross from right-back Bacary Sagna,
The visitors, though, had to make an early change when Flamini pulled up with what looked like a groin problem and was replaced by Gnabry.
After dropping off for much of the opening 15 minutes, Palace found some energy when Thomas - once on the books at Arsenal - darted down the left and his deep cross was headed over by Bannan.
Arsenal were soon back on the offensive as Gnarby played in Ozil, but he looked to square the ball through the six-yard box instead of shooting.
Chamakh - sold by Arsenal in the summer - tested Szczesny with a dipping 20-yard effort as the Eagles again looked to take the match to the Premier League leaders, with Bannon's curling cross then just ahead of Damien Delaney.
Santi Cazorla almost had Arsenal in front when the Spaniard spun onto an angled pass through the Palace box and sent a low shot across the face of Julian Speroni's goal.
The Palace goalkeeper then stood up well as Ramsey got in at the near post to drill an angled shot at point blank range.
Arsenal had a penalty claim denied just before half-time when Delaney bundled over Gnabry right on the chalkline. Both referee Foy and his assistant signalled for only a free-kick, which came to nothing.
There was no debating a key decision at the start of the second half when Guedioura cut down Gnarby, and this time all the officials were in no doubt.
Arteta crashed the penalty past Speroni, into the left corner, to give the leaders some breathing space.
It was almost 2-0 straight away when a clearance from Delaney bounced off Gnarby and just an inch past the post.
Arsenal were reduced to 10 men after 65 minutes. A long ball up field was taken on the chest by Chamakh, who looked to get clear before tussling with Arteta, shoulder to shoulder just inside the Arsenal half.
The pair went down in a heap, but that was enough to convince Foy the Gunners captain had denied his former team-mate a clear goalscoring opportunity and went for the red card.
Wenger replaced Gnabry with Wilshere as he looked to protect the slender lead before, after 72 minutes, Spain defender Nacho Monreal came on for Cazorla.
Szczesny made two brilliant saves to kept Arsenal ahead when he first touched a thunderous 20-yard effort from Ward against the goal frame and then, from the resulting corner, produced a brilliant one-handed stop to turn over a dipping strike from Jedinak.
Monreal, deployed on the left of midfield, ghosted into the penalty area with some fine close-control, before his shot at the near post was blocked.
Arsenal finally secured three points when Ramsey broke down the left and delayed a chipped pass through for Giroud, who arrived on cue to nod the ball past Speroni.