The injuries weren't the issue, his lifestyle was. He didn't have the motivation or discipline to stay in shape, and completely let himself go during his injuries. His lifestyle caught on with him, he was never a very dedicated hardworking athlete. When he was young that wasn't an issue, but at that age it becomes a problem. It wasn't untill this year that he dedicated himself to get in shape again for the World Cup, the only thing that could still motivate him, especially after van Gaal took his captaincy and completely dropped him from the squad. He was skinnier than he had been in 8 years probably, and I just read that out of all players at the World Cup he covered the most distance in those 6 games. Ofcourse being in shape doesn't mean you regain form immediately, he still lacked that.