Borussia Monchengladbach striker Mike Hanke has undergone groin surgery in a bid to clear a long-standing problem before the start of the season. The former Germany international pulled up in training on Thursday and, after consulting with the club\'s medical staff, it was decided that an operation was the best way to resolve a problem which has been troubling him through pre-season. According to a club statement, the operation was successful and Hanke will be sidelined for several weeks. The 28-year-old will now work on recovering in time for the start of the season on 25 August. Hanke scored eight goals for the Foals last season, helping them earn a place in the UEFA Champions League.