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Liverpool 2 Arsenal 1
It is just as well that Arsenal do not lose often, for they do not deal with defeat at all well.
Sunday's defeat was only their second in their past 55 in the Premiership, but it means that, since their 49-game unbeaten run in the Premiership came to an end at Old Trafford, they have won just one in six and trail the leaders Chelsea by five points.
It was Neil Mellor who finally scored the winner, his splendid swerving shot from just outside the box eluding the dive of Jens Lehmann to give him his first Premiership goal and Liverpool a deserved victory.
So outplayed were Arsenal that they failed to win a single corner, and their equaliser came from their only meaningful attack. "We looked like we were suffering from fatigue," Arsène Wenger said.
"Liverpool were sharper than us. I still don't feel there's a lot wrong but when you don't get results, things become wrong and that's where we need mental strength."
Much was made last season of the way Arsenal had developed a toughness following the disappointment of squandering an eight-point lead to Manchester United the previous year but, phenomenal as they were, it is debatable just how much resilience was required in a campaign in which they never trailed in the final 20 minutes of any game.
The feeling endures that Arsenal are bad losers in both senses of the term. The repercussions of the post-match ill-feeling at Old Trafford rumble on, and so too does the disruption to Arsenal's equilibrium.
Robert Pires and José Antonio Reyes look shadows of the players they were two months ago, and Cesc Fabregas, forced into regular action by injuries to Edu and Gilberto Silva, also wears a tired look.
The real midfield concern for Arsenal, though, is that Patrick Vieira, after collecting his fifth booking of the season for a foul on Xabi Alonso, will miss the meeting with Chelsea in a fortnight. "At the moment it means we are very short," Wenger said. "It will be a big problem for us to miss one more player."
Only Liverpool's perennial inability to finish sides off kept Arsenal in the game so long. The failure to convert possession into goals is hardly a new phenomenon at Anfield but the problem was exacerbated by the absence through injury of Milan Baros, Djibril Cisse and Luis Garcia.
Under Rafael Benitez, Liverpool have few problems in generating a head of steam, merely in directing it.
Arsenal were hardly in the game in the first half but it was only four minutes before the break that they fell behind.
Harry Kewell was generally as ineffective as ever, but when he headed Steve Finnan's long pass down for Steven Gerrard, Mellor's diagonal run drew Sol Campbell out of position, and the Liverpool captain laid in Xabi Alonso to sidefoot into the top corner.
The equaliser in the 57th minute was of equal quality, Vieira exchanging passes with Thierry Henry and Pires before flicking a deft finish over Chris Kirkland. Arsenal, though, could only keep reason at bay for so long.
Wenger spoke of his irritation at the way his team have begun dropping points in games in which they should not, but he could hardly group Sunday's defeat in that category. His side were well-beaten, and their slide is gathering pace.