Sunderland are keeping tabs on Thomas Gravesen's situation at Celtic.

The Black Cats and Sheffield United are eyeing the Dane, whose agent John Sivebaek said: "It's never good to have so much speculation about your future in the media, but he can't do anything about it.

"But Thomas has two years left on his contract and he would love to be at Celtic for that time but you never know in football.

"However, I have not heard anything about any bids, you would have to ask Celtic because the bids will go to them first."