The Liverpool skipper returned to the starting line up against Manchester United last Saturday for his first start since March when he damaged his groin against the same opponents.
Six months of rehabilitation along with surgery and an infection in the area resulted in some dark days where he feared his playing days were numbered.
I think it's only natural that you have doubts," said Gerrard. "Different things cross your mind from time to time.
"When I got the injury I knew it was going to be a serious one, something that I wasn't used to. I had to try to be positive. I'll admit that I was down, as low as I've ever been as a footballer.
"Before the operation I'd been getting niggles and having injections to play. Basically I knew I wasn't right.
"I was fighting to get fit, just to get out on the pitch. I was trying to put my body on the line. But it wasn't the real me and I wasn't the player I want to be.
"I was missing training sessions and coming in the day before a game trying to get that last session in, or having injections to play the next day.
"You can only do that for a certain amount of time before your body gives in, and mine gave in. My groin packed in on me.
"Without a doubt the last six months have been the hardest of my career."