Nike fell out with Manchester United long before last week's announcement they were severing ties.
The Daily Mail describes the relationship as "rock bottom", with Nike to have one final year as United's kit sponsors before adidas take over.
With their period of negotiating exclusivity with Nike at an end at the turn of the year, United exercised their right to talk to other companies and invited Adidas, Warrior and Puma to Carrington in successive days late in January.
But what really annoyed Nike was the way United laid out huge banners carrying their rivals' logos on the centre circles of Carrington training pitches.
With Carrington still a Nike-branded training centre, officials from the US-based firm saw the temporary displaying of Adidas, Warrior and Puma signs as deliberately and unnecessarily provocative.
