The fans' joy of watching their Arsenal team get the better of Manchester City was tempered a little bit after Arsene Wenger confirmed Alexis Sanchez had suffered a setback in his hamstring injury.

Sanchez was expected to be named on the bench for this big English Premier League encounter at the Emirates, but the Chile international failed to make it to the squad, raising questions over his fitness.

After watching Arsenal beat Manchester City 2-1 thanks to goals from Theo Walcott and Olivier Giroud, Wenger revealed the worrying news, with the manager ruling out the forward for the entire festive period.

"I think he will be back [only by] January 10," Wenger said. "Christmas period, you can't count him."

Arsenal already have enough injury problems, with Santi Cazorla, Francis Coquelin, Jack Wilshere, Tomas Rosicky, Mikel Arteta and Danny Welbeck all long-term absentees, and Sanchez's return from a hamstring problem picked up in the game against Norwich City late last month would have been a welcome one.

However, Wenger now has to make do without his premier forward, even if others, specifically Joel Campbell, has stepped up admirably.

"Two days ago, he had had a slight [setback], but yet he planned to be on the bench tonight because he is so keen," Wenger added on the Sanchez situation. [However], he got a little bit of a pain and we didn't take a gamble."

Arsenal travel to the south coast to face Southampton – a team that has given them a difficult time in the recent past – on Boxing Day, before hosting Bournemouth and Newcastle United either side of the New Year.

Having picked up a well-deserved victory over Manchester City, a win which took them back to within two points of Leicester City, while also increasing the gap from Manuel Pellegrini's men to four points, Wenger will not want his team to lose momentum.

"It is too early to say we can win the league but it strengthens our belief," Wenger said of a match that Arsenal controlled for the majority. "You come out and realise you have earned your right to win these games and for us it is important.

"We have to be ready to fight like that in every single game and you do that quite [often]. It is quite interesting on my side there is real life in the team, real togetherness and real solidarity, so let's take care of that."