Barclays Premier League leaders Liverpool fought back to take a draw from a high-octane match with an Arsenal side who had striker Emmanuel Adebayor sent off.
Robin van Persie had fired the Gunners ahead with a fine strike on 24 minutes, only for former Tottenham Hotspur striker Robbie Keane to equalise.
Adebayor was shown a second yellow card by referee Howard Webb on the hour mark, and the Gunners had to settle for a draw which further dents their fading title aspirations.
Liverpool looked to extend their lead at the top of the Barclays Premier League without manager Rafael Benitez, who did not travel to Emirates Stadium following surgery to remove kidney stones.
The leaders were, of course, set to present a stern test of those credentials and it was a cagey opening to the match.
The first decent chance came in the ninth minute.
A long ball up field was knocked back by Keane from the edge of the Arsenal penalty area into the path of Reds captain Steven Gerrard, whose 20-yard effort was straight at Manuel Almunia.
A clipped ball in from Bacary Sagna on the right floated through to Emmanuel Adebayor, but his glanced, diving header just lacked the power to beat Jose Reina.
clearly rattled
Keane was in the book on 20 minutes for clattering in from behind on Gael Clichy out on the left touchline.
Arsenal then snatched the lead through Robin van Persie out of nothing after 24 minutes.
Nasri chipped a high ball through from just inside his own half, which the Dutchman, on the edge of the Liverpool penalty area, collected on his chest before turning two defenders and firing a right-foot shot into the net.
Liverpool, whose form has dipped in recent weeks, were clearly rattled after previously looking quite comfortable.
In contrast Arsenal were now playing with a renewed confidence and held possession well.
On 33 minutes, Gerrard tried his luck with a long-range free-kick, but it was too central to trouble Almunia.
Adebayor was cautioned for leaving his foot in as he went for a 50/50 ball with Insua before Liverpool levelled minutes before the break.
The ball was thumped upfield from deep inside the Liverpool half by Alvaro Arbeloa and bounced right over Johan Djourou into the path of Keane.
knee problem
The Republic of Ireland striker let the ball bounce again into the Arsenal penalty area before lashing it past Almunia.
The Reds almost snatched another ahead of half-time, but Gerrard was unable to get on the end of Dirk Kuyt's low ball across goal.
Arsenal captain Cesc Fabregas had suffered what looked like a knee problem in a tackle with Spanish compatriot Xabi Alonso at the end of the first half, and was unable to continue.
Abou Diaby came on to play on the left of midfield, with Denilson and Alex Song in the centre.
Liverpool started strongly, with Almunia having to beat away a snap-shot from Lucas.
The tempo of the match increased as the hour approached, but it was the visitors who remained in the ascendancy as Agger headed wide following a corner.
Referee Howard Webb reduced Arsenal to 10 men after Adebayor was shown a second yellow card for a challenge on Alvaro Arbeloa, who fell to the ground clutching his face.
To their credit the Gunners responded by pressing Diaby further forwards as they looked to get back in front.
Nasri sent a 25-yard effort wide, then Almunia saved bravely at the feet of Kuyt as the visitors pressed for a winner.
Agger fired a superb 25-yard strike just over as both teams had to settle for a point.