Speaking to the media, Parkinson said: "I think Ollie is closing in. I just wanted to make sure Ollie got through this week in training and the signs are looking positive, and he'll be back in a couple of weeks. We need Ollie back, he's a key player for us. He was instrumental for us last year.
"He's a player who has played in the Championship; first year did well, second one was a difficult one at Rotherham because they had a very weak squad. But he's played at this level and when he signed for us, he was determined to get back into the Championship.
"His start to the season has been curtailed but obviously he's a very naturally fit player and the sooner we get him back involved in football, the better. His energy and his quality, I can't wait to get Ollie back out with us."