The Scotland forward handed in a transfer request at Molineux on Wednesday and the Black Cats manager has admitted that his team are having a problem scoring goals
Having been relegated with Wolves last season, Fletcher feels his future still lies in the Premier League and has handed in a transfer request at the Championship club, confirming on Twitter that his 'head has gone'.
However, Wolves are refusing to part ways with their top goalscorer from last season until their valuation of the 25-year-old is met, and have already rejected bids.
Whether Sunderland have made a bid or not is yet to be revealed but O'Neill has admitted that he is looking to bolster his attacking options having seen his Sunderland side struggle for goals in pre-season.
Speaking to Sky Sports News, he said: "We have certainly in pre-season found it a bit of a problem scoring goals.
"But I think we can rectify that."
The Scotland international was one of the standout players for Wolves last season; despite their relegation he still managed 12 goals in the Premier League.