Arsenal boss Arsene Wenger will have a "little word" with Alexis Sanchez to make sure the forward is in the right zone to inflict pain on former club Barcelona tonight.

The Gunners face a daunting task when they come up against the reigning European champions in the opening leg of their Champions League first knockout round at the Emirates Stadium (7.45pm).

Wenger's men have fallen at this hurdle in the previous five seasons and many will expect that to become six as the collective attacking talents of Lionel Messi, Luis Suarez and Neymar are unleashed in north London.

One player who could have been lining up for the visitors is Sanchez - but the Chile international instead was sold to Arsenal in the summer of 2014.

He has since flourished under Wenger, becoming an integral member of a side which has won back-to-back FA Cups and remain in the hunt for three trophies this season.

But, while Wenger admits the 27-year-old will be keen to show his former employers what they are missing, the Frenchman wants Sanchez to manage his temperament on a big night for the club.

"He will be fired up, but that doesn't mean he will be in the right zone," Wenger said.

"The performance zone is where you are focused and relaxed and that is what is difficult in sport.

"Sometimes when you are too focused you are not relaxed, so it's a zone where everything looks easy and sometimes when you play against your former club you are not necessarily in that zone."

Asked if he would have a chat with Sanchez to emphasise his point, Wenger replied: "A little word, yes.

"He can help us to win the game. But I know that not one player will win us the game. We need a top level team performance where everybody is spot on in the discipline and sharp physically and ready to work for the team.

"If everyone does that then maybe Alexis can make the difference but it's not especially on him. We need all our players."

While Wenger opted to completely rest the likes of Petr Cech, Aaron Ramsey and Mesut Ozil for Arsenal's 0-0 FA Cup fifth-round stalemate against Hull on Saturday, Luis Enrique kept his main men in the side which beat Las Palmas in the Primera Division.

He did make changes to his side but insists he will run the risk of upsetting supporters by playing his key men if and when he desires.

"Yes and I did them, I rotate," Enrique replied when asked about a lack of alterations on Saturday.

"I made the decisions that I thought were best for my team. I'm a decision maker and I make decisions constantly every two or three days, whether my decisions are liked or not is something I can't control."