Bruno Fernandes was reportedly furious with Mason Greenwood for his lackadaisical display in training this week.
The Red Devils had just one session between their Champions League defeat by Istanbul Basaksehir and the 3-1 win over Everton this weekend.
Manchester United teenager Greenwood came off the bench late into the match in Europe and was expected to start against the Toffees.
But Solskjaer left the Englishman out of his 18-man squad, claiming Greenwood was suffering with illness.
According to The Times, there is growing concern over Greenwood's application, and Man United star Fernandes was said to have been pretty disappointed with the youngster's recent performance in training.
Greenwood is alleged to have refused to have ran for a pass during a training match in Friday's session, prompting an outburst from Fernandes.
This isn't the first time the fiery Portuguese has hit out at a team-mate, with Fernandes voicing his frustration at compatriot Alex Telles just two weeks into his United tenure.
There was no argument between Fernandes and Greenwood, but the incident comes amid more general concerns about the teenager's application.
Greenwood was reportedly given a warning for arriving late to training in October, just months after he was sent home from England duty for breaking coronavirus protocols.
England boss Gareth Southgate left Greenwood - who made his international debut in Iceland - out of his upcoming Three Lions squad as punishment.
Manchester United maintain that the youngster's lethargic performance in training was down to Greenwood suffering with illness.
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