The Arsenal boss is set to throw Sanchez back into his starting line-up ahead of schedule against Crystal Palace tomorrow.
Sanchez was given extra time off after winning the Copa America with Chile and has only been back in training for two weeks.
But he was pictured running on the beach during his holidays, and did extra drills after the defeat to West Ham last weekend, when he came on as a second half sub.
And Wenger is tipping him to be even better than he was last season, when he scored 25 goals after joining the club in a £35m transfer from Barcelona.
"He's a hyperactive guy and he needs that to be happy," said Wenger.
"I'm a bit worried but on the other hand I knew once he would be here he would be difficult to stop, so I gave him a long enough break.
"He had four weeks off, which is quite reasonable. He has impressed me. He works extremely hard in every training session to show that he is ready.
"What he does is for me normal, what everybody should do. He made 52 or 53 games last year and the Copa America so he has an instinct that tells him how far he can go.
"In March, April, May last season you could see he was a bit jaded. But once he's out there he always gives 100 per cent.
"He came back from the Copa America reasonably fit. He practiced for two weeks before he came back. He didn't start from zero. In training now he looks alright.
"I believe that last year he came in a bit late after the World Cup and this season he knows what is expected of him and he will do better than last year.
"He's very ambitious. He wants to win when he goes out there. He knows he won the FA Cup. He wants to get more now. He's a winner."
Wenger also revealed how Jack Wilshere could be back from his latest ankle injury in half the time Arsenal feared.
Wilshere suffered a hairline fracture to his right ankle in training and it was feared he could be out for two months.
But Wenger said: "He is back in training. We thought it would be six to eight weeks. But it could be three to four. Quite positive.
"Maybe when younger we overplayed him sometimes because he's such a good player but now we are quite cautious with him."
However, the news is not so good for Tomas Rosicky, who could be sidelined for more than two months, while Danny Welbeck will be out for another three weeks.
