Manchester United technical director John Murtough fell out with Ralf Rangnick towards the end of the caretaker manager's time in charge.
Rangnick left United at the end of the season for the Austrian national team job.
The BBC reports the pair's relationship ended up breaking down to the point they were "barely on speaking terms".
Rangnick hit out in April that the club needed "open heart surgery" to get back on track.
Those words aren't thought to have gone down well with football director Murtough, who believed Rangnick did not try to protect the club's reputation.
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