The former Real Madrid striker has been ruled out with an eye injury but hopes to play some part in Schalke's match against Mainz on Saturday before travelling to Istanbul
The Netherlands international was forced to pull out of his national side's match against Italy last Wednesday, but hopes to be able to play some part against Mainz in the Bundesliga this weekend, ahead of the European tie in Turkey.
The striker admitted he faces a race against time to be fit for the domestic fixture, but revealed his recovery is going well.
"It's not that bad. The recovery will take a bit longer though. It still has to improve. That always takes a while with these kinds of injuries," he told Voetbal International.
"I would like to get going again. I'll try to be there when we face Mainz on Saturday and play if I can, but it will be tight. It will be a race against the clock."
The 29-year-old scored four goals in the Champions League group stage and is seen as one of coach Jens Keller's key players.