“I wasn’t supposed to be back in until next week but I felt good and turned up at Wast Hills, which surprised the manager,” Grainger told the B'ham Evening Mail.
“I had a little run and my knee and hamstring were okay, and I joined in yesterday. In fact, I’m raring to go.
“Generally, I’m quite fit, I just need games to get my sharpness back.
“If he wanted to throw me in for the Cup tie that would help, but I wouldn’t like to guess how long I’d last.”