Attacking midfielder Morrison, the standout performer in United’s FA Youth Cup triumph last season, made a 20-minute cameo appearance for the first team during the Carling Cup victory at Aldershot last month.
But the 18 year-old aired his displeasure at being left on the bench during the 2-0 win against Everton at Altrincham’s Moss Lane by tweeting “---- take” and “I can not waite [sic] till the end of the season” shortly after the final whistle.
Manchester United team-mate Rooney hit back at Morrison by tweeting to the teenager that the end of the season “might come sooner than u think!!!!!”
Morrison, whose progress has been affected by off-field problems including avoiding jail in May following his second conviction in four months, replied to Rooney by tweeting: “What do you mean :/” after appearing to backtrack on his earlier tweets by insisting that “end of season means holiday time.”