Mario Gotze has upset Bayern Munich shirt sponsor and shareholder Adidas by wearing a Nike T-shirt on his official presentation by the club.
Bayern confirmed that they had apologised immediately to Adidas, but the international sports manufacturer was compelled to express its dissatisfaction at the incident.
"These pictures have surprised us negatively," Adidas spokesperson Oliver Bruggen told Abendzeitung. "That's a breach of contract, because that was an official appointment by Adidas partner FC Bayern."
Bayern press officer Markus Horwick added: "We failed to see that shirt because of the hectic day. It won't happen again."
Gotze's agent, Volker Struth, claimed that Nike had asked the player to wear the garment, something a spokesperson for the company denied had anything to do with an attempt to gain publicity, saying: "That's beyond our influence."
The media uproar overshadowed Bayern's unveiling of their €37 million signing from Borussia Dortmund, a player whom sporting director Matthias Sammer described as an obvious addition to a side that had just won an unprecedented Treble.
"This is a good day for FC Bayern," Sammer said. "We thought about making an addition to our central offence. Our coach has a clear concept of the type of player he wants to work with and so it was a fast decision to approach Mario Gotze."
Gotze said he had already spoken to Pep Guardiola about his role in the team even though injury will prevent him from making an immediate impact during pre-season.
"The first contact with Guardiola was something really special," Gotze said. "He mainly asked how I feel and explained a bit of his philosophy to me. I want to achieve a lot with the team and play great football here."
Of the injury that prevented him playing against Bayern for Borussia Dortmund in the Champions League final, he added: "It is clear that I would prefer to be on the pitch with my team-mates but I hope to start running next week."
Arriving with the burden of a sizeable transfer fee has weighed heavy on the shoulders of some players, but Gotze is looking forward to repaying the €37 million that Bayern paid for his services.
"That's a great sign of appreciation," he said. "I can deal with that well."
Meanwhile, Sammer said that Mario Gomez is yet to strike a deal that will see him move away from the Bundesliga champions, despite his agent claiming he is bound for Serie A with Fiorentina.
"The cards are on the table, but we have not reached a satisfactory agreement," he said.