Arsenal failed to strike a deal for the 20-year-old last month but, though he hopes the attacker stays for the near future, Clemmens Tonnies believes he will eventually leave.
The 20-year-old was the subject of a late bid from the Gunners last month after a delegation was sent to Germany to negotiate a big-money move for the playmaker, though the Bundesliga club rejected the offer.
Speaking at SpoBis, a sports business conference in Dusseldorf, Tonnies stressed he would love to see Draxler continue his development in Gelsenkirchen for the next two seasons but conceded the Germany international would eventually move on.
"We can not keep a super talent like Julian forever. But it also wouldn't be fair to refuse players to jump on the train that is waiting for them," Tonnies is quoted as saying by SID. "We are often talking. I told him he should stay with us another two, three years and that a move would be too early for him now."
Tonnies also moved to alleviate concerns that Draxler could become the latest Germany prospect to join runaway Bundesliga leaders Bayern Munich, adding: "He won't go to Bayern, I know that."