Alexis Sanchez, with only three goals in 23 games since his move from Arsenal in January, was axed for Saturday's game at West Ham; Marcus Rashford has been rebuked for failing to warm down correctly after a Champions League game.
The Hammers fully deserved the result, with their revival continuing following a shaky start to the season, while Jose Mourinho's side seem to be going in the opposite direction.
Keown said, "He's a wonderful talent - we know that - but something is just not quite right with him", he told Match of the Day.
Mourinho redirected the question from a Spanish reporter to the journalist that wrote the story, joking at a packed press conference that he had "put a bug on my telephone".
"Every player is different, no player is the same", he said.
"If you want the truth I think it was honestly horrendous".
Rojo is also still unavailable for selection as he continues to work his way back to full fitness from a knee injury that's hampered him in recent weeks so it means Mourinho will be without four senior players for the Valencia clash.
With things looking increasingly negative for the former Chelsea coach, it is no surprise that Zinedine Zidane - three-time Champions League victor as manager of Real Madrid - is being linked with the job.
Jurgen Klopp defends out-of-form Mohamed Salah
Maurizio Sarri's men saw their ideal start to the season end last Sunday, following a 0-0 draw at West Ham. "It's really cool. You could see the first ball he missed a bit it was not in the right position, and the next ball he passed! Why?
Luke Shaw branded it "horrendous" claiming the players were completely to blame after Manchester United lost 3-1 to West Ham at the London Stadium on Saturday.
Reporter: "That he needs to create more".
Mourinho said: "Exactly, (it) is a collective thing, the reason why we don't win is responsibility of everybody". "The reason why we don't win matches is the same reason we win matches - it is the responsibility of everybody".
The manager might argue he needs better support in the transfer market from executive vice-chairman Ed Woodward to have a serious chance of revival, but the fact is Mourinho has more than enough talent to do much better.
Their relationship became totally strained the other week though when, after the draw to Wolves, in which Pogba gave the ball away for the away side's equaliser, Pogba criticised the way the team played saying, "We are at home and we should play much better against Wolves".
"I like that perspective, but I don't agree totally".
"When I arrived here immediately I had the feeling he's a very good player for my way of football because he's a centre-back who is very technical".
"When we win, we all win".