“I had it for the majority of last season and, to be honest, I was struggling through games. It affected some of my performances. I couldn’t do as much as I wanted to do in some games and it was frustrating," Samuel told the Birmingham Evening Mail.
“What I’ve got to do now is rest up as much as possible, and do some exercises to try to strengthen the muscle.
“If rest doesn’t make things right, then I’m going to have to look at something else and there is the possibility of an operation, but hopefully rest will do the trick.
“It’s a pity as it’s always a pleasure and an honour to be called up by the under-21s, but the main aim for me now is to be ready for July 8th when we report back for pre-season training.
“Hopefully I’ll be fit for then because we all want to be firing when the new season gets underway with a new manager in place to impress.”