Wenger: Sanchez will be even better
The 26-year-old was a surprise inclusion on the substitutes' bench for last weekend's Barclays Premier League opener against West Ham, having just returned to training following an extended summer break, and came on for the closing 23 minutes of Arsenal's surprise 2-0 home defeat.
Sanchez kept himself in shape during an enforced holiday following Chile's Copa America triumph by going through fitness drills on the beach while the rest of the Gunners squad were away during a pre-season tour to Singapore.
It is such dedication which Wenger believes gives Sanchez the physical capability to last the distance over what is expected to be another gruelling campaign.
"I am a bit worried, but on the other hand, I knew before the start that once he is here, he would be difficult to stop, so I gave him a long enough break," said Wenger, who is expected to start Sanchez at Selhurst Park on Sunday.
"He had four weeks off, which is quite reasonable. He finished on July 3 and he came back on August 3.
"Alexis works extremely hard in every single training session to show that he is ready.
"He came back as well reasonably fit. He practiced for two weeks before he came back. He did not start from zero and in training now, he looks alright."
Wenger added: "I think what he does is, for me, normal. It is what everybody should do.
"You wonder if he has created a beach at home, and runs along the living room. He is a hyperactive guy. He needs that to be happy."
Wenger, though, accepts Arsenal will have to guard against potential burnout.
"He made 52 or 53 games last season, plus the Copa America, so that means somewhere he has an instinct that shows how far he can go," Wenger said.
"It is difficult. In March, April, May (2015), you could see he was a bit jaded, but he is still a guy who can make a decision in a game, and once he is out there he gives 100 per cent.
"He is very ambitious, Alexis. He knows he won the FA Cup, now he wants to look to get more.
"This season, he knows what is expected from him, and he will do better than last year."
While Sanchez has given Arsenal a welcome fitness boost, forward Danny Welbeck is no nearer a return from the knee problem which ruled him out of the FA Cup final and England's end-of-season internationals.
"It is much slower than expected," Wenger said.
"It was a bone bruising at the start. You think that it will be quite quick.
"Danny is an important player for us and the fact that he is not available is a bit of a concern.
"They have done all kinds of scans that today are very sophisticated and some of them I don't understand at all, but they tell me no (operation is needed).
"(At the moment) he is (training) in the gym."