Jan Vertonghen
Tottenham Hotspur defender Jan Vertonghen being monitored by Manchester United Reuters

Manchester United are reportedly keeping track of out-of-favour Tottenham Hotspur defender Jan Vertonghen and could make an approach for the Belgian during the January transfer window.

According to the Mirror, Louis van Gaal is a keen admirer of the former Ajax skipper and could make a move in a bid to solve the defensive crisis at United.

The Belgian international has endured a difficult time under new manager Mauricio Pochettino, starting only six of Spurs' 11 games this season.

The defender's unhappiness is an open secret at the club, but the player still has three and a half years in his contract and will not force a move away, but has hinted that he could leave when he rejected a new improved contract earlier in the year.

The report claims that Pochettino was not impressed with the defender's attitude and hence axed him for the home game against Stoke City, which they lost 1-2 before the international break.

It is believed that the 27-year-old Belgian defender was not happy when he was overlooked by the manager for the club captain's role, which was given to Younes Kaboul.

The Old Trafford club have had a torrid time with their defence this season, and the manager is having to field inexperienced youngsters, due to the injuries suffered by first-team defenders Phil Jones, Jonny Evans and Marcos Rojo.

The Red Devils have been linked to various replacements and apart from Vertonghen, Van Gaal is also keeping tabs on Aston Villa's Ron Vlaar, who played under the United boss for the Netherlands national team and also Mats Hummels, who was the rock in Germany's defence during their victorious 2014 World Cup campaign.

The Villa defender is the cheapest option as he is on the final six months of his contract and will be available for much lesser than the other two defenders.