Greenwood was left out of United’s match day squads for the recent wins over Newcastle United and Paris Saint-Germain, with Solskjaer saying that the 19-year-old striker was struggling with a minor injury.
Solskjaer dismissed suggestions that Greenwood’s absence was due to disciplinary reasons though reports later suggested that the youngster was being punished for poor time-keeping.
The United manager refuted that at his Friday morning pre-match press conference ahead of Chelsea’s visit to Old Trafford, taking aim at both the press and former United players who have suggested otherwise.
"I'm not concerned at all with Mason making a target of himself," Solskjaer said. "He came in, played fantastic, played against Tottenham in the first league game, was brilliant, and kicked on.
"Yeah, he made a mistake with England and suddenly the whole English press go after him and that’s something we have got to look after.
"He’s a fantastic boy to work with. I have to disappoint you, he's never ever late for training, he's never a problem on the training ground. I’ve seen the stories, I've seen some ex United players talking about him and they don't know what they're talking about.
"We have got photographers outside the training ground every day, so they can see every day he’s on time. I don’t know where these stories have come from.
"He's got a good family behind him, he has had a good background in the academy and he's a good trainer. He trains really well and I cannot believe all these stories about him not being professional.
"That's something that we have to deal with with many players, many other players at United have had that."
The United manager did not reference any ex-players by name. Dimitar Berbatov called on Greenwood to “stay in the right lane” after he was sent home from an England national team camp for breaching coronavirus protocols in September.
Solskjaer said that he expects Greenwood to only develop further after establishing himself as a fully-fledged member of United's first-choice starting line-up.
"We have a great record and tradition and history of bringing our players through, that means from early on you get good habits," the United manager said.
"We trust you, you can express yourselves. Mason's come through this programme, he has done fantastic and he will be kicking on I'm sure. Of course he's a very exciting boy to work with."