Black Cats boss Ricky Sbragia said, “It’s not quite worked out for Roy up there. It was going well, but he got suspended and found it difficult to get back in the team.

“It would have been unfair to leave him there.”

O’Donovan’s departure could determine whether or not Kevin Smith, whose loan deal at Raith Rovers is about to expire, returns to Tannadice.

United boss Craig Levein wouldn’t be drawn on that subject, preferring to concentrate on Saturday’s clash against Celtic at Parkhead.

And the United gaffer feels his side will have to produce a season’s-best display if they are to win at the home of the current champions, who will have been buoyed by their 1-0 Old Firm win over Rangers at Ibrox last Saturday.

However, United have similar reasons for being optimistic about their prospects, having turned in an impressive display of their own in beating Falkirk last time out.

And Craig feels if they can reproduce that sort of performance, they’ll certainly be in with a shout of plundering the points.

He said, “I thought we were excellent against Falkirk last weekend and we’ll need to keep that sort of form going at Parkhead if we are going to give ourselves a chance of winning. We’ll probably need to produce our best performance of the season if we are going to do it.

“Celtic are on a high because of their win last weekend, but we’re in good form as well, so the lads have plenty of confidence. As ever, I can’t say whether we’re going to do it, but, one thing’s for sure, we’ll go there all guns blazing and give it our best shot.”

Craig confirmed midfielder Greg Cameron can go out on loan when the transfer window opens.