Manchester United forward, Alexis Sanchez, was involved in a furious training ground row with academy graduate, Mason Greenwood, with angry words exchanged between the pair, the UK Sun reports.
Sanchez is desperately trying to build up his fitness, after returning from the Copa America with a hamstring injury.
In one of his first training sessions back at the club, the Chilean was fouled by the youngster, leaving the 30-year-old fuming.
Sanchez was left out of the squad against Chelsea, but he is back in training and can be expected back in action sooner rather than later.
Greenwood, 17, came off the bench during the 4-0 win over Frank Lampard's side on Sunday and is set to get a chance to shine in the first team this season.