Sunderland's worst fears have been confirmed after Jonny Williams was ruled out for a month.
The Wales international, on a season-long loan from Crystal Palace, came off injured after just 30 minutes of the 1-0 defeat to QPR at the weekend.
Scans have revealed Williams will now be missing for up to four weeks with a grade two tear in his quad.
Sunderland fans haven't seen the best of the 24-year-old after an injury-hit season, which has already seen him miss three months following surgery for a dislocated shoulder.
Williams had only recently returned to first team action and he now faces another lengthy spell out.
Coleman said: "Jonny will be out for a month.
"It is a grade two tear in his quad. That’s disappointing because it has been a tough season for Jonny, very stop-start.
"I can’t get him fit and keep him fit and that’s a shame because he is such a good player and in full flow as a Sunderland player the supporters would love him.
"We haven’t managed to see that because unfortunately he has had bad luck."
There was brighter news for fellow midfielder Darron Gibson, who has been out with a groin injury.
He returned to training at the Academy of Light on Tuesday for part of a session but Coleman has confirmed he remains a few weeks away from a first team return.
Coleman, who has also had Ty Browning ruled out for the season, added: "Darron Gibson trained in part of the session but he will be a few weeks away.
"Even before you can play in a behind closed door game or an under-23s game.
"He is doing well, he has had no setbacks so far."
Sunderland are bottom of the Championship with just nine games left to avoid successive relegations following relegation from the Premier League last season.