Owen Hargreaves has claimed that former club Manchester United treated him like a "guinea pig" in their attempts to get him back to fitness.
The midfielder was released from Old Trafford over the summer following three injury-plagued years before signing for rivals Manchester City.
"I've had to be a guinea pig for a lot of these treatments," the 30-year-old told The Guardian. "But when you're left to try to make something of a difficult situation, it's not really an option to say: 'Let's sit it out and rest for six months.'"
Hargreaves has also said that he was unfit to play in his comeback game against Wolverhampton Wanderers last November, a match in which he lasted five minutes before coming off with a hamstring problem.
"I started that game with two muscle injuries but I should never have been in that position to begin with. I was just going to try to get through 45 minutes because that would have been a start," he added. "But I didn't even last five.
"There were 70,000 people there and, if I had walked away from the game, it would have looked like I didn't want to play. I thought: 'I'll try to play, I just won't sprint.' I know it sounds comical."
The former Bayern Munich player scored on his City debut in their 2-0 Carling Cup win against Birmingham City on Wednesday night.