Berlin - A mysterious thigh strain is overshadowing Arjen Robben's final few months at Bayern Munich, leaving the injury-prone winger frustrated on the sidelines.
The 35-year-old, who scored the winning goal for Bayern in the 2013 Champions League final at Wembley, has said this will be his tenth and final season at the defending Bundesliga champions with his contract to expire in June.
However, Robben has not played since scoring two superb goals in the 5-1 home rout of Benfica last November in the Champions League's group stages, and his absence shows no sign of ending.
The mystery injury has ruled Robben out of Bayern's upcoming matches, especially next Tuesday's Champions League last 16, first-leg tie at Anfield against Liverpool, which "annoys us - and him the most" said head coach Niko Kovac.
The Dutchman is particularly frustrated because he was on the verge of a comeback last month, saying "everything is going to plan, no problem" at the time. But since then his thigh is refusing to heal, mystifying both him and Bayern's medical staff.
"It is very, very frustrating," Robben, who has won the Bundesliga title seven times with Bayern, told Friday's edition of German daily Bild.
"It's not going well, we are trying everything, but at the moment, it's not good.
"The exact problem is that one doesn't know exactly what it is. It is really difficult.
"You try everything, you do everything. Twice I was really close to being back in the team again, but then there were setbacks.
"It's not easy for the head, especially when you feel good in yourself.
"My last game (against Benfica) is a good example of that and I have the feeling that when I come back, I will play like that."
Having gone public on his decision to leave Bayern this June, Robben is weighing up his options, but recently rubbished reports of interest from Japanese side FC Tokyo.
"Maybe I'll just stop (playing)," he told German magazine Kicker recently.