Alexis Sanchez has been told by Arsene Wenger to respect his Arsenal contract, with the forward's return to the club set to be delayed by illness.

Sanchez was due to report for pre-season training on Saturday (AEST), having been given extended leave after international duty for Chile at the FIFA Confederations Cup.

With Sanchez entering the last year of his contract at the Gunners, clubs including Bayern Munich, Paris Saint-Germain and Manchester City have been linked with a move for the 28-year-old.

But Wenger, who has been clear he will keep Sanchez at Arsenal and risk losing him for nothing at the end of the season, insists the attacker will stay, although his return has been postponed until Tuesday.

"He has flu. I had him on text yesterday saying he would come back as soon as possible," Wenger said after Arsenal's 5-2 Emirates Cup win against Benfica on Sunday (AEST). "We're in touch with him and his doctor.

"There's no problem except he won't come back tomorrow, he'll be back on Tuesday. There's no development. It's always the same. He's staying, of course. I think the players who want a new contract have to respect their contract.

"For a manager it's a bit different, it concerns. What is the future of the club, what's going on, what's happening, it has great uncertainty. For the player it's different.

"I can't reveal to you what he says, I cannot reveal what is a secret conversation. We speak in English. He's flying back as soon as he's in a position to fly back. He has the flu. That's normally four or five days."

Theo Walcott struck twice as Arsenal brushed aside Benfica with a second-half blitz, but it was new left wing-back Sead Kolasinac, a free transfer from Schalke, who caught Wenger's eye.

"Kolasinac has gone from strength to strength in pre-season," Wenger said. "Every single week he moved his level up and today he was influential. Kolasinac looks powerful and the timing of his availability looks very good."