Ruben Amorim claims Marcus Rashford failed to adapt to his training and matchday demands at Manchester United. Rashford, 27, did not play in 12 successive matches for United before he joined Aston Villa on loan for the remainder of the season on Sunday.
Villa are covering at least 75% of Rashford's £325,000-a-week salary and have an option to buy the England international in the summer.
United are expected to move for a proven goalscorer in the next transfer window. Rashford didn't play for United after he was substituted in the 2-1 Europa League win against Viktoria Plzen on December 12.
The England international did not acknowledge Amorim when he was taken off in the second half with United 1-0 down. Three days later, Rashford and Alejandro Garnacho were omitted from the squad for the Manchester derby victory at City on account of their attitude.
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