Mats Hummels
Mats Hummels admits clubs are 'knocking on his door' but is unperturbed by interest in him [Getty]

Borussia Dortmund skipper Mats Hummels remains unfazed amid increasing speculation linking him with a move to Manchester United.

The Germany international has again been identified as one of United's priority transfer targets by media reports during the January transfer window.

Dortmund's miserable domestic campaign, which sees them sat second from bottom as the season approaches its halfway point, has helped fuel talk of a possible January exit.

But Hummels, 26, says he is now used to clubs expressing their interest in his services.

"There are always clubs knocking on my door, telling me they are interested," Hummels told Sky Germany. "But I have always decided that I don't want to do it."

While Hummels has yet to be swayed by offers to leave Dortmund, the towering centre-half has opted against making a long-term commitment to the club, having entertained the idea of leaving the Westfalenstadion in the future.

The former Bayern Munich youngster went on to reiterate that stance, adding: "I think I have always made good decisions and that I will continue to do so. I have never said I will stay here until 2024 or even 2030 and have stayed regardless.

"I prefer to continue on the path to not promise anything but in the end maybe just do it [stay at Dortmund] than to say that I'll stay and then just leave."

While United conceded just six goals in their 10 game unbeaten run – which was brought to a halt by Southampton on Sunday 11 January – the club's frailties at the back have been a particular concern this season.

While United manager Louis van Gaal has indicated he would prefer to wait until the summer to make significant additions to his squad, the club continue to be linked with a commanding centre-half. Atletico Madrid's Diego Godin and Aymeric Laporte of Athletic Bilbao are also understood to have been considered.