Arsene Wenger admits he has concerns over the discipline of Granit Xhaka, who has added extra steel to Arsenal's midfield this season.
Switzerland international Xhaka arrived at Emirates Stadium from Borussia Monchengladbach tasked with toughening up what some felt was the costly soft underbelly of the Gunners.
Xhaka has impressed in the early stages of his Arsenal career, scoring a stunning goal against Hull City in September, but the other side of his game was also evident when he saw red for hacking down Modou Barrow in a 3-2 win over Swansea City last month.
With Sunday's often fiery north London derby against Tottenham looming, Wenger concedes Xhaka's temperament is an issue which could see the midfielder left on the bench.
"I've no specific idea what I'll do [with the starting XI] but I am concerned [with his discipline] yes," Wenger said.
"Discipline is important and we want to be effective in the situations we face in a derby. I think he's quite a composed and calm guy, sometimes on the field the reaction is a bit impulsive.
"He needs to work on that and his control in the game."
One man earning praise from Wenger recently is Mesut Ozil, who scored a sublime solo winner against Ludogorets in the Champions League on Tuesday.
Reports in Germany suggest the attacker may be rested by his national side for their upcoming matches - a World Cup qualifier against San Marino and a friendly with Italy - and Wenger believes that would be a sensible option.
"I got noise of that. I think it would be an intelligent decision," he said. "We have to wait until he [Joachim Low] gives out his selection. We need to wait and see."
Arsenal go into Sunday's derby at the Emirates joint top of the Premier League with Manchester City and Liverpool, with Spurs three points behind in fifth.
Wenger revealed on Thursday that Kieran Gibbs is a doubt with a shoulder injury, while the fitness of Santi Cazorla, Theo Walcott and Nacho Monreal will be monitored. Hector Bellerin is expected to be fit.
The Gunners have seen promising starts falter in November in recent years, and Wenger hopes history will not repeat itself.
"It's exciting, we have an opportunity to show that we are ready for a chance and to do better than we have done historically," he said.
"It's a good opportunity on Sunday to show that.
"We've started November in a positive way and I'm sure we can face the history but we have as well an opportunity to make history and show better than what we did before."