Arjen Robben has been ruled out of action for \"several more weeks\", according to Bayern Munich following the Dutch winger\'s successful operation on a troublesome groin injury last week. Robben went under the knife last Friday in Germany after the injury flared up and ruled him out of the Netherlands\' final UEFA EURO 2012 qualifiers. Bayern said last Friday that Robben could return to training in around a fortnight, but on Thursday coach Jupp Heynckes indicated the Dutchman would need at least a month before starting to train with a ball. \"Arjen [Robben] has to have another two weeks of rest followed by two weeks of light training before he starts running again,\" Heynckes said on Bayern\'s website. \"We\'re not in a position to say when he will return. I think it will be several weeks yet.\" Robben has already missed several matches for Bayern this season due to a succession of injuries. The 27-year-old returned to action for Bayern late in the match against Bayer Leverkusen on 24 September, scoring once in the 3-0 Bundesliga win. He started on the bench the two following matches, coming on as a 90th-minute substitute during the 2-0 UEFA Champions League defeat of Manchester City and then playing the second half in a scoreless draw with Hoffenheim. Robben\'s absence has not prevented Bayern from making an impressive start to the season. The Bavarian giants have lost only once in eight matches and conceded only one goal, scoring 21 to lead Werder Bremen and Borussia Monchengladbach by three points. Bayern host Hertha Berlin on Saturday.