The veteran coach is delighted with the German's rate of recovery after ankle surgery, and is hopeful that the striker will soon be fit for selection
The Germany international sustained an ankle injury in pre-season, but after a successful operation the 27-year old is almost ready for a return to the pitch.
"He has trained very well," Heynckes told AZ.
"He came through pain free and I think that and he could finish the first part of the final training session with the team on Saturday, but no one can forecast when he will be back in the squad."
Last year's Champions League runners-up could have also received positive feedback on Arjen Robben's recent thigh injury, but the Dutchman has been ruled out of Sunday's clash with Bayer Leverkusen.
"For Sunday, there's no way, because he has not trained with the ball and the team," he continued.
"I hope that he'll be back training with the ball soon. He will possibly be available for the DFB-Pokal again against Kaiserslautern next Wednesday."
Bayern Munich are currently top of the Bundesliga after winning their first eight games of the campaign.