As reported by The Sun, Fellaini filed litigation at London's High Court, claiming the New Balance boots he wore as part of an endorsement deal caused him "loss of enjoyment, inconvenience and impact on performance" and asking for £2.1 million.

Fellaini, who signed the endorsement deal while playing for Everton, said the boots needed to be "steamed and stretched" by equipment managers before he could wear them, and that he made repeated complaints to the company.

New Balance reportedly countered by saying Fellaini had told the company the boots were "perfect."

In a statement provided to ESPN on Monday, New Balance said it was "confident that it has acted appropriately."

"Although we cannot comment on pending litigation, New Balance can confirm that the company plans to vigorously defend itself and its longstanding record of manufacturing excellence and surpassing the needs of athletes around the world," the statement said.

"New Balance is confident that it has acted appropriately and is grateful for the services historically provided by Mr. Fellaini."

Fellaini's legal team did not immediately respond to ESPN FC's request for comment.