Keegan: Barton did nothing wrong

Barton - who was recently released early from a jail sentence following a conviction for assault and affray - was sent on for the closing minutes and he was immediately in the thick of the action, with a strong challenge on Samir Nasri. The France international then appeared to trip Barton off the ball, and was cautioned.

Keegan, who had words with Nasri and Arsenal captain William Gallas at the final whistle, said: "Joey has done nothing wrong. I'm concerned about my team, not individual players."

He added: "Joey came on, got a good tackle in on Nasri. Then the guy sliced him down. That's what happened and that's what I saw, which is what I was upset about.

"I like Nasri very much - he's a player we looked at for a possible signing but you can't do that. If it had been the other way round, I wonder what the reaction would be. I know the referee didn't see it but the linesman did and it should have been a red card."

Keegan, though, accepted Arsenal's class came through in the end, with a double from Robin van Persie and Brazil youngster Denilson.

"We came up against a side who had to bounce back from a poor result," he said. "We needed a break, which we did not get, like when Nicky Butt's header hit the bar, but there is no denying they are an excellent side - the only thing they are fighting for is where they will finish."

Arsenal manager Arsene Wenger, meanwhile, hailed his team's "complete" performance as they continued from the midweek Champions League qualifying win over FC Twente.

"I am very pleased with the performance, both offensively and defensively. It was a complete one, there was great balance in the team, with movement," he said.

"Apart from at the start of the second half, we were always in control and played the game we love, and showed the way we can play."