Jadon Sancho will reportedly demand to leave Borussia Dortmund during this summer's transfer window if the German club refuse to sanction his exit.
BVB are thought to value the former Manchester City youngster in excess of £100m, though, which United are unlikely to pay due to the financial impact of the coronavirus outbreak.
"In these scenarios, once you've agreed with the player and the player obviously has indicated his desire to leave and join you, then it usually helps in terms of the player's insistence at his current club with regards to: 'I want to leave, I know what I'm going for, I know what I'm doing, so if you don't allow me to leave then I will agitate'," McGarry said on the Transfer Window Podcast.
"And this is a player who has had three separate incidents in this season so far of fines for misbehaviour in terms of the club code of conduct and we know that Dortmund at different times have said that he's been a bit problematic in this season because of the unsettled nature of his season, because of the interest mainly from Manchester United."
Sancho enjoyed an excellent 2019-20 campaign for Dortmund, scoring 20 times and contributing 20 assists in 44 appearances in all competitions.