Aubameyang is approaching the final 12 months of his contract at the Emirates.
Xhaka, who was replaced by Aubameyang as captain during the season, admits his exit would be a damaging blow to the club.
“If that were to happen, it would, of course, be a great loss for the team and the club," he told SportBild.
“Auba is always dangerous and always good for a goal, and as a guy, he's also really great.
“He is always positive, optimistic, helpful and very professional."