Wayne Rooney insists the injury that effectively killed off United's season, could land World Cup glory for England. The striker's twisted ankle, suffered in the Champions League quarter final first leg against Bayern Munich in March, sounded the death knell for United's European and Premier League hopes. He failed to score another goal for Sir Alex Ferguson's side, having hit 34 to that point. It saw Chelsea overtake them at the top of the table, while Bayern knocked them out of the Champions League on away goals. But despite failing to get on the score sheet in Monday's 3-1 win against Mexico, Rooney believes the lay off will see him return to his best in South Africa. Of course I always want to score, but if it doesn't happen I'm glad it's in a friendly and not in the World Cup, he said. Hopefully I'm saving them up for South Africa. It has been a long season for everyone and, of course, players can feel jaded. But I'm quite fortunate because I haven't trained a lot in the last six weeks. I will have another full week's training in Austria and I felt good against Mexico. I had a bit of a stiff neck after the match, but that should pass. Fingers crossed, my break out injured this season will be of benefit during the World Cup. I have trained in every session with England and there is no problem with my ankle. You have to hold back sometimes in tackles in training. It can be difficult, but you must be careful not injure yourself or your teammates.