The striker will be allowed to come off contract next month.
Sanllehi told arsenal.com: "In ways it is quite similar to the Aaron (Ramsey) situation. This summer we were in talks with him to see if [he would stay or go], he had several offers, he decided to continue in the club until the end of the contract.
"We respected that. We knew that he was going to add a lot to the club over the last year, but again, we were in the last year of contract so it was a very similar situation."