Arjen Robben has expressed his frustration at the injury which has interrupted his final season with Bayern Munich, and admits he still doesn't know when he will return to first-team action.

Robben has registered five goals and two assists in 15 competitive appearances for Bayern this term, but has been sidelined since the UEFA Champions League win over Benfica at the end of November due to a thigh injury, while subsequent complications with the sciatic nerve have hindered the 35-year-old's comeback bid.

"It's not going well," Robben admitted in an interview with German daily Bild. "We're trying everything, but nothing's working out at the moment.

"Unfortunately, it's one of those where you don't know the exact problem. It's difficult, and very frustrating.

"I was pretty close to making my comeback twice before, I was back with the team, but then there were more setbacks. It's not easy mentally."

Where's Arjen? Bayern's Flying Dutchman isn't expected to be fit to face Liverpool at Anfield in the Champions League next week. - 2018 Getty Images

Frustration aside, Robben remains confident he will hit the ground running once he is back to full match fitness, and cited the Benfica game in which he scored two of Bayern's five goals as an example.

"I played well, felt good out there," he recalled. "I have the feeling I'll continue in much the same vein once I'm back."

Earlier in the season, Robben confirmed that the 2018/19 campaign will be his last as a Bayern player.

Watch: Remind yourselves what Bayern are missing with Arjen Robben's top 5 Bundesliga goals

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The Dutchman has scored 143 goals and provided 101 assists in 305 competitive appearances since joining Germany's record champions from Real Madrid in 2009.

He will be looking to add to his collection of seven Bundesliga titles, four DFB Cups and the 2013 UEFA Champions League, before ending his ten-year association with the club in the summer.

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