Southampton's midweek 1-0 win against Chelsea in the Under-21 Premier League Cup was the 27-year-old's first match in 291 days.
Forster damaged his left patellar tendon after falling awkwardly in March's Premier League clash with Burnley and has been on the long road to recovery every since.
"Obviously, (I was) a bit rusty, but it was perfect," the keeper said after his return.
"I'm buzzing to get 90 minutes under my belt - it's probably been nine-and-a-half months now.
"I'm just delighted, just to kind of get through it, and the victory makes it that much better."
Forster was quick to thank Southampton's medical staff after playing the full 90 minutes against Chelsea's youngsters.
The goalkeeper made a fine save to deny Kasey Palmer after Ryan Seager gave Saints the lead in a match which he suggested could be the first of several appearances for the development squad.
"It's stage by stage, one day at a time," he told Southampton's YouTube channel.
"We've done everything correctly for the last nine months and not rushed.
"We've done it step by step and that's how we'll continue to the end.
"There's no rush. I just want to make sure I get it right and when that day comes it will come.
"It will be good to play a few more 90 minutes, get that under my belt and just go from there, but like I said we're looking step by step, day by day and we'll see where it takes us."