The former Arsenal goalkeeper was unavailable for Martin's final five games after fracturing his finger during Southampton's 2-0 defeat at Wolves.
"We all let the gaffer (Martin) and Gilly down," Ramsdale explained. "We didn't perform at our best, not through anything other than it just didn't work for us.
"We didn't stop trying, we didn't stop running. I came to the club mainly because of the manager, and not being able to play under him because of my injury, I felt like I'd let him down.
"That's one of the things I was saying to him - if I could have played earlier I would have, but the risk was too high and the surgeon said no.
"It's been really tough for me and something I've had to try and work on and help the boys off the pitch. It's the first time I've missed football through injury.
"I've had experiences at both ends of the table, and I'd have loved to be out there the last few weeks, through good times and bad times, but it was a hard month."