Manchester United tried to sign Mats Hummels of Borussia Dortmund and Sporting Lisbon's William Carvalho in the frantic final week of the window, sources have told ESPN FC.

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United spent more than 150 million pounds, which was a record for any club in a single window. Despite that, they were prepared to spend even more, as manager Louis van Gaal still wanted to bring in a commanding centre-back and midfielder.

The initial top target as regards the latter was Juventus' Arturo Vidal, but doubts over the condition of his knee meant the club were reluctant to spend a huge fee on a player who may have required an incentivised contract.

ESPN FC was also told that another early primary target was Hummels. United had made an enquiry about the Germany defender in June only to be firmly rebuffed by Dortmund, but the English side broached the possibility again when negotiations began over Shinji Kagawa's return to the Westfalenstadion.

United suggested Hummels could be exchanged for 20 million pounds and the Japanese midfielder, but Dortmund again rejected the idea and ultimately signed Kagawa for eight million euros.

United also attempted a similar partial swap deal for Carvalho on deadline day itself, offering Anderson and a fee. Sporting Lisbon were not interested, and sources state that the player himself was still holding out for a move to Arsenal, due to their participation in the Champions League.

United also made a tentative enquiry for Nigel de Jong of AC Milan that went nowhere.

Van Gaal retains some concerns over his midfield, and would have gone for Roma's Kevin Strootman in the summer were it not for the midfielder's need to recover from a serious knee injury. The 24-year-old suffered damage to his anterior cruciate ligament in March, which cost him a place in Van Gaal's Dutch World Cup squad.

The United manager is said to now be content with their summer work, after a huge acceleration in business over the past two weeks. Sources say that came after a summit meeting the day after the 2-1 defeat to Swansea City in their Premier League opener, during which Van Gaal pressed home the need for reinforcements. United ended up signing four players in the final two weeks, in contrast to just two before that.

Van Gaal told De Telegraaf that, when he had been in a similar situation after taking over at Bayern Munich, club president Uli Hoeness had demanded answers.

Bayern, like United, collected only two points from their opening three games in the 2009-10 campaign and the Dutchman told the newspaper: "At around the same time at Bayern, I was called in to explain myself. By Hoeness. But you know what the people at United do? They just keep buying! They support me! They have faith in me! You can feel that, as a person, too."

There is now expected to be further expenditure in January.