LONDON (AFP) - Manchester United are facing further defensive problems, with an injury to Ashley Young prompting a possible move into the January transfer market for manager Louis van Gaal.

Young is to undergo groin surgery after suffering an injury during United's 1-0 win at Liverpool last Sunday.

The former England international, 30, who has performed as a winger and as a full-back for United in recent games, may now miss much of the remainder of the season.

And with Luke Shaw, Antonio Valencia, Marcos Rojo and Phil Jones currently all out injured, van Gaal is running out of options with Matteo Darmian the only fit senior full-back available.

"He (Young) has to have an operation so he will be out for a long time," van Gaal said on Friday. "It is not just a month or so but longer and we already have big problems in the full-back positions.

"It's unbelievable. We are not lucky with that.

"I need full-backs. The difficulty is that we ask for a level. We are looking but it is not so easy and nobody can understand that."

Cameron Borthwick-Jackson is expected to replace Young at left-back against Southampton on Saturday, when United will also be without the injured midfield pair of Michael Carrick and Bastian Schweinsteiger.

United have put together an unbeaten five-match run following a four-match streak either side of Christmas to ease the pressure on van Gaal.

That has not stopped speculation regarding the Dutchman's position, following suggestions he may look to end his Old Trafford stay a year early at the end of the season.

United also moved to deny reports that a delegation from the club had met with outgoing Bayern Munich coach Pep Guardiola, who is expected to move to Manchester City before the start of the new season.