The Republic of Ireland striker made just one Premier League start last season, and was one of those expected to leave this summer as Keane revamped his squad.

But Connolly has had surgery which will keep him out for four months - which seems certain to rule him out until after the August transfer window closes.

And that makes it highly unlikely that any new club would risk signing him in the summer.

Keane confirmed to the Gazette: "Dave had a hip operation the other day, so he'll be out for three-to-four months.

"It's a blow for him, but at least he will be fit early in the new season."

If Connolly is unable to move in the summer, he would have to wait until the transfer window reopens in January before he can move on.

In the short-term he could go out on loan to a Championship side once he has fully recovered, but that was not something which appealed to him last season.

The only other alternative is for Sunderland to pay up the remaining year on his contract and release him, which would allow Connolly to join another club outside the transfer window.

Keane said a few weeks ago that he is considering paying up several players this summer, but it remains to be seen whether Connolly is one of them.

And the downside is that they would then receive nothing for a player who cost £1.9m when he joined from Wigan back in August 2006.

Connolly was the club's top scorer with 13 goals when Sunderland won promotion from the Championship 12 months ago.

But after making a handful of appearances, but just one start, at the beginning of last season, he dropped out of contention.

His only Premiership start was against Birmingham City last August.

A couple of Championship clubs expressed an interest in taking him on loan, but he opted to remain on Wearside.

In total, he has made 42 appearances and scored 13 goals for the Black Cats in all competitions.

It is not unheard of for clubs to buy players making their way back from injury - Sunderland bought Andy Reid from Charlton while he was still recovering from knee damage.

But with Connolly having been out of first-team action for almost a year, his situation is different.

And Connolly himself might prefer to stay and see out the third year of his contract, just as he did with his second.

Despite his lack of recent first-team action, Connolly was one of five Sunderland players included in new Ireland boss Giovanni Trapattoni's 40-strong preliminary squad last month for a training camp in Portugal and then for friendlies against Serbia and Colombia later this month.

But his injury means he has not been included in the final 28-man squad, named this week.

Andy Reid, Liam Miller and Roy O'Donovan were named in the party which headed to the Algarve for the training camp this week.

Anthony Stokes was also included in the preliminary squad, but did not make the cut, and was also left out of the Republic of Ireland Under-21 party which travelled to Malaysia for the Intercontinental Cup tournament this week.