Victor Valdes must prove himself playing for Manchester United's Under-21 side before he can begin to think about replacing David de Gea in the first team, says Louis van Gaal.

Valdes, 33, signed an 18-month contract with the club in January and has featured as an unused substitute in seven games.

The Spaniard has appeared twice for Warren Joyce's Under-21 in that time however, with Van Gaal regularly allowing players to feature for the club's second string as part of their returns to full fitness.

"He has to do it in the second team," Van Gaal said when asked about Valdes's chances of earning a start in the first team.

"Like Ashley Young is doing that, like Michael Carrick has to do that. It is always the same. I think it is normal."

Valdes featured in his first game since March 2014 when he started in goal for United's Under-21 side against their Liverpool counterparts in January. The Spain international completed his rehabilitation from a severe knee injury at United after being invited to train with the club in late 2014.

Rafael da Silva and Ander Herrera have also featured for United's second string in their returns from injury earlier this season with a similar plan in place for Carrick.

Carrick, 33, was ruled out for four weeks with a muscle rupture at the end of January and while he initially made quick progress in his recovery, Van Gaal revealed last Friday (13 January) the midfielder had suffered a minor setback.

The news was an unfortunate timing after Daley Blind suffered an injury in last Wednesday's win over Cambridge United. However, Van Gaal will not rush Carrick straight back into the first team.

With both United's holding midfielders expected to miss Monday's FA Cup fifth round clash with Preston North End, Wayne Rooney could fill in once again at the base of midfield. The England international filled that role after Blind went off injured last week, earning praise from his manager in the process.