Sunderland boss Roy Keane has highlighted Ross Wallace as one of their early season successes.
He said: "Ross has been different class for us with his tackling, his workrate, his fitness levels and his desire. If we trained for eight hours a day I would still probably have to drag him off the training ground.
"I saw Ross when I was at Celtic. He didn't look happy in himself but he was always bubbly, always having a laugh. He always enjoys training and that rubs off on people. Hopefully he will have a big role to play this year."