Manchester United are unhappy with Phil Parkinson following comments made by the Wrexham manager about the challenge from goalkeeper Nathan Bishop which left Paul Mullin in hospital, sources have told ESPN.

Parkinson hit out at Bishop after the United goalkeeper charged out of his penalty area and collided with Mullin, leaving the Wrexham striker with a punctured lung.

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He branded the challenge "reckless" and said he was "fuming" to lose his star forward for the start of the season.

Sources have told ESPN that United believe Parkinson's comments are irresponsible and have inflamed a situation which has already taken its toll on Bishop.

The 23-year-old was booed relentlessly by Wrexham fans after the incident and looked visibly shaken as he left the stadium. He was substituted at half-time, although United manager Travis Binnion insisted afterwards that was always the plan.

Sources have told ESPN that United are concerned Parkinson has opened up Bishop to online abuse.

Bishop tweeted an apology to Mullin after the game and reached out to him directly via other Wrexham players.

He posted: "Just wanted to share my sincerest apologies to Paul Mullin.

"A complete misjudgement and a genuine accident with zero malicious intent at all! Wishing you the speediest recovery and hope to see you back scoring goals as soon as possible."