Robin van Persie and Louis van Gaal were reportedly good friends before the ex-Dutch national team boss joined Manchester United.
But according to the London Evening Standard, 'cracks' are now appearing in the their relationship as Van Persie becomes increasingly wary of Van Gaal following the deal to bring Radamel Falcao to the club.
Van Persie played an important role in helping to recruit Van Gaal to Old Trafford over the summer, and was a key man for Holland at the World Cup - then coached by the Dutchman.
But the report claims during the tournament the Manchester United striker found it increasingly strange that Van Gaal opted to sub him over other options through the competition.
Van Persie was replaced in every group game, played 90 minutes against Costa Rica but was again taken off in extra time in the semi-final against Argentina.
There has been speculation in the newspapers that claim Van Persie has a lingering knee problem that will ultimately require surgery - something the player has swiftly denied.
“I can honestly say I will not visit a hospital any time soon to undergo surgery,” Van Persie told reporters.
Sir Alex Ferguson
But there's a feeling that he's not fully fit yet, although of course that could be a hangover from the World Cup. His injury record is not the best though, and he missed a large chunk of time last season after picking up a knee injury against Olympiakos in the Champions League.
Van Gaal sanctioned the move to bring Falcao to Old Trafford on deadline day, but it raises questions as to how the United manager will be able to fit in his three top forwards - Falcao, Van Persie and Wayne Rooney.
Rooney may drop into midfield, but he's been vocal in the past about playing in his favoured position further forward. As club captain it is unlikely that he will be demoted, which means van Persie and Falcao may be competing for the same spot.
And with no European football this season, it's not as though van Gaal needs the extra squad players to rotate.