The centre half was unable to prevent Dortmund slumping to a 1-0 defeat at home to Augsburg which leaves them sitting rock bottom of the Bundesliga, two points adrift of safety.
A video emerged of Hummels accompanying goalkeeper Roman Weidenfaller to the caged fence where the home fans were sitting, urging them to calm down.
Hummels admitted after the game he wasn't surprised by the fans' reaction and said: "If one is in this position after 19 games then it would be unacceptable not to have understanding for the fans' reactions."
But the defeat merely served to raised the spectre that Hummels could well leave the Bundesliga in the summer.
United courted Hummels last month, but it would take an offer in excess of £30m to claw him away from Dortmund.
Hummels is one of a handful of defensive targets on Louis van Gaal's radar and it remains to be seen whether Dortmund can keep hold of him.
GETTY
Mats Hummels confronts angry Dortmund fans
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