Louis van Gaal may still be focused on Netherlands' progression in the World Cup, but his new employers, Manchester United, are well underway in the pursuit of their top transfer targets this summer.

With Ander Herrera and Luke Shaw having already been snapped up, Borussia Dortmund's Mats Hummels could well be the next man in line to don the red jersey.

The German has become one of the most highly-coveted centre-halves in world football, and he is a central figure to both his club and country.

United are looking to bolster their defence with Hummels, as well as various other areas of their squad.

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Click here for the SIX players to follow Hummels to United

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Memphis Depay

So far this summer, PSV’s Memphis Depay has had to make do with substitute appearances in the Netherlands’ World Cup campaign, but he has managed two goals and one assist in this time. Depay has shown positive signs when called upon, using his pace to trouble defenders later on in the game as they tend to tire.

Manchester United struggled with goals from all areas of midfield last season, and Depay’s record last season – 12 league goals – shows that he could bring a goal threat to United’s attack. His relationship with Louis van Gaal could likely see him follow Hummels to United this summer.

William Carvalho

United’s courtship of the Portuguese midfield powerhouse has been in action for over a year now. The 22-year-old is rumoured to cost around £35 million if van Gaal is to acquire his services.

Carvalho didn’t feature as prominently as he may have hoped to have done this summer, only playing 90 minutes in Portugal’s final 2-1 win over Ghana. With Marouane Fellaini believed to be surplus to requirements, Carvalho’s physical presence will be needed in the United midfield.

Eliaquim Mangala

The young Frenchman has yet to feature for his country this summer, with the experience being used more as a learning curve for the future. Nevertheless, Mangala has cemented his reputation as one of Europe’s hottest young centre-backs and will cost in excess of £30 million this summer if United are to seal the deal.

Mangala has become a central figure in the heart of the Porto defence, demonstrating maturity and an ability to read the game far beyond his tender years. Manchester City and Chelsea are believed to be interested, but United’s need could see them sneak ahead in the race for Mangala.

Angel Di Maria

Despite what was an outstanding season for Di Maria, Real Madrid look ready to allow the Argentine to leave in order to secure the signing of James Rodriguez. He will doubtless have copious admirers from across Europe, and van Gaal is believed to be interested.

Di Maria hasn’t lit up the World Cup as he regularly does in the white of Madrid, but his 118th minute goal against Switzerland saw Argentina progress through to the quarter-finals. A naturally left-footed player who can play anywhere in midfield, Di Maria’s technical prowess is a must-have for United heading into the new season.

Bastian Schweinsteiger

Astonishingly, Bastian Schweinsteiger is only 29 years of age, despite being around for what feels like an eternity. And the classy Bayern midfielder is rumoured to be out of favour with Pep Guardiola in Munich.

Last season United lacked any kind of cutting edge from their midfielders, too busy passing the ball sideways and not willing to push the game on. Schweinsteiger’s hawkish vision would add what their central midfield lacked last season. Despite a few injury concerns, Schweinsteiger has years ahead of him, and is at the top of his game.

Thomas Vermaelen

Arsenal’s skipper has very much been a bit-part player for the past 18 months for his club. The partnership of Per Mertesacker and Laurent Koscielny has pushed him to the fringes, and he is looking to leave in order to secure more first-team action ahead of next season.

Vermaelen is a proven performer in the Premier League, and was widely considered as one of the country’s top centre-halves until recently. Despite his relative lack of height at under six feet, Vermaelen overcomes this with an incredible leap, which has in the past seen him rack up a handy goal tally. Rediscovering his best form will only come with game time, and United look likely to offer him this.