Bayern Munich's Franck Ribery needs two months out - including France's World Cup play-offs against Ireland - to recover from a persistent knee injury, his doctor said on Thursday.

Ribery consulted Professor Jean-Henri Jaeger in this eastern French city on Tuesday and the specialist said France's playmaker could be out for at least two months - twice what had been expected.

Jaeger said an operation on the chronic tendon injury in Ribery's right knee could be carried out if treatment failed.

"It's one month's treatment, plus one month's rehabilitation.

"So that means two month's minimum before Ribery returns to the game," the specialist. "If it works, he will be able to play again. If it does not work, it will require surgery."

However Jaeger said he did not know yet if Ribery would follow his recommendations.

The 26-year-old has struggled all season and Bayern coach Louis van Gaal has insisted Ribery needs an extended break.

"We have made the decision that we want to allow him time for the injury to heal properly," said the Dutchman.

Ribery is set to miss France's two-legged play-off qualifiers against Ireland on November 14 and 18 as well as Bayern's forthcoming Bundesliga games away to Stuttgart and at home to Schalke as well as Leverkusen.

The knee tendon injury, which hindered Ribery's pre-season preparations, flared up again on October 3 in the 0-0 draw with Cologne and the Frenchman has not played since.

Van Gaal admitted they missed the midfielder during Wednesday night's 2-1 Champions League defeat in Bordeaux.

"Without Ribery we have lost our creativeness," he said.

France's deputy national coach Alain Boghossian sounded resigned to losing Ribery for the World Cup qualifiers.

"Bayern does want him to have an operation. They are mulling it over ... but for me, Frank is all but out for the play-offs," Boghossian said in Bordeaux.