LONDON -- Arsenal will have Shkodran Mustafi back fit for Friday's Premier League game against Liverpool, but Arsene Wenger would not say whether that means returning to a back-three formation.

Mustafi has been out since limping off during the 3-1 defeat to Manchester United, and Wenger has switched to his more familiar back-four system in recent games with a shortage of available centre-backs.

But he is ready to return on Friday as Arsenal look to avenge the embarrassing 4-0 loss at Anfield in August, increasing Wenger's tactical possibilities.

"[Mustafi] should be fit to be available for Friday night," Wenger said. "I haven't decided [the formation] yet, but the fact that we are adaptable now to both systems [means] it will be down to me to make the decision, do we play in a four, or in a three, or in a five?

"I have to analyse that well. And as well, you have to guess a little bit who will play [for Liverpool]. It's not always the same, it depends on their personnel. They have plenty of offensive players, and looking at them recently, they have changed their teams a lot. So it's difficult to guess. But for me the most important is that we turn up with a positive performance."

Shkodran Mustafi has not played for Arsenal since the Premier League defeat against Manchester United. Stuart MacFarlane/Arsenal FC via Getty Images

Wenger also insisted he would not be afraid to start Ainsley Maitland-Niles in a left-back position against Mohamed Salah, with the 20-year-old academy product having been picked ahead of Sead Kolasinac in the last two Premier League games.

Kolasinac started in Tuesday's Carabao Cup win over West Ham, but Wenger said both players are in contention against Liverpool.

"Both of them are quick and strong and good. Kolasinac will be available for Friday," he said.

The game will mark the return of Alex Oxlade-Chamberlain to the Emirates after he joined Liverpool in a £40 million deal just days after Arsenal's drubbing at Anfield.

Oxlade-Chamberlain started in that game despite the uncertainty about his future, and he was among the players who was most heavily criticised for a lacklustre performance, but Wenger did not want to single out that decision as his main regret from the game.

"It would be not fair to put the defeat at Liverpool, where the whole team had a bad performance, on one player," he said. "On the other side, you analyse did you make mistakes or not? You cannot go home and say everything was perfect when you lose like we did."

Oxlade-Chamberlain is unlikely to get a friendly reception on his return, but Wenger insisted he wants all former Arsenal players "to be respected" by the crowd.

Arsenal are one point behind fourth place Liverpool, and Wenger acknowledged that the games between the top six could be more important than ever this season in determining who will finish in the Champions League spots. But this game is also a chance to set things right for the Gunners after that Anfield humiliation.

"When you have such a long career as I've had you have some defeats, unfortunately, that hurt you for the rest of your life. But I believe what is interesting in football is you have always a time a to make up for it. And when you can put things right, do it," Wenger said.

"So let's focus on what is in front of us, and turn up on Friday with a completely different performance."