"The manager did the sensible thing with me (against United)," Gerrard told Liverpool's official website.
"It was hard to sit and watch from the bench, but I'd only had on full training session.
"My heart was saying I was desperate to play, but there are another 40-50 games hopefully this season.
"I wasn't ready to start. I'd been training on my own for the last 10 days. The most I could have played was 20-25 minutes.
"I'll have a few more sessions under my belt before Tuesday's game in Marseille and will be in better shape, but it'll be the manager's decision."