William Gallas has hit back over claims he is not fit to captain Arsenal and insists winning a trophy this season will vindicate his appointment.

The 31-year-old had been criticised for his lack of leadership as the Gunners suffered defeats against Fulham and Hull while his own form was questioned in the wake of the 4-4 draw with Tottenham last month.

Gallas was also recently pictured coming out of a nightclub with an unlit cigarette in his mouth but the France defender remains unmoved, even after he was praised for his role in last weekend's crucial victory over Manchester United.

"I know people were talking about my leadership before the game but what I found interesting is that after we beat United everyone was saying my leadership was good," he said.

"But for me I played the way I have been all season. In fact, I think I had a better game against Spurs a couple of weeks ago but no one mentions it.

"That's how it is in football, though, people only look at the result and because we beat Manchester United we are getting all the praise again. That's why I always say that at the end of the season, the only thing that will matter is whether you have won a trophy - the rest is forgotten if you can win it."

Gallas reserved praise for Samir Nasri's recent Premier League form.

The 21-year-old scored both goals in the 2-1 win against United to continue a fine start to his career in north London following his £15.8million summer move from Marseille.

Nasri's immediate impact has helped cushion the blow of the continuing absence of Tomas Rosicky and Gallas said: "Samir scored both our goals and I was very pleased for him.

"He has fitted in really well since he came over from France - he has picked up the language well and you can see that on the pitch the Premier League is suiting him perfectly.

"He is a very strong player, too, and is always up for the challenge and he showed at the weekend again that he can get goals for us, too."

Perhaps the key factor in their victory over United was the Gunners' relentless work-rate throughout the side.

Defeats against Fulham, Hull and Stoke prompted questions of the side's desire to prove their hunger for the fight and Gallas challenged his team-mates to repeat the manner of victory over United when Aston Villa visit Emirates Stadium on Saturday.

"What I really liked about last Saturday was how hard everyone worked," he added. "We really put pressure on them for the whole game and you saw the result. Maybe we haven't done that enough this season.

"We have shown we can do it against United, so why can't we do it in every game from now?"

The momentum from beating United continued in fine style as Arsenal's youngsters cruised to a 3-0 Carling Cup victory over Wigan on Tuesday night and defender Johan Djourou stressed the importance of keeping the feel-good factor around the club.

"People think Arsenal have a very young side that cannot win trophies but the first team are showing that with a young team we can do it," said the Swiss centre-back.

"And on Tuesday night, with an even younger team, we did it again. The mood at the club is fantastic now.

"When you lose the mood goes bad but when you win everything is back together.

"We need to win games and try to be invincible. We lost some silly points but now we have bounced back and we have to keep going."