The 28-year-old Belgian has been linked with a move to Manchester United.
"At the moment Thomas Vermaelen is here. He is injured at the moment with a short-term injury. It could happen, yes it's a possibility that he goes. If he goes we have to replace him because he's an important player in our squad," Wenger told a news conference.
"I expect him to stay but he, of course, did not play enough games last year. For me he's a very important player but I couldn't guarantee him the games he wanted last year."
He denied reports that he was trying to sign Porto playmaker Juan Fernando Quintero but said further moves in the transfer market were possible.
"I am very happy because I did what I wanted and I am still hoping to do more," he said.
"We are a bit ahead of what we usually do because the availability on the market was bigger than before. I think 15-30 August will be busy again."
- Sports & Recreation
- Thomas Vermaelen
- Manchester United