He could still be plying his trade back in Germany next campaign.
"Nothing is decided yet," he told German magazine Kicker. "Fulham can activate a clause, and I also have to agree.
"As things stand now, I will return to Cologne in the summer. But I have to consider and talk to both clubs.
"I wanted to become a starter (at Fulham), and I managed to do that. I am proud I have become a fans' favourite. But of course I can still do better, and that's what I am trying to do."