Manchester United manager Jose Mourinho says "some [players] care more than others" at the club after their failure to win any of their past three games.
In their last two league matches United have drawn with Wolves and lost to West Ham, slipping to 10th in the Premier League table as a result.
They were also knocked out of the Carabao Cup by Championship side Derby.
Asked if he was worried about his position if the side's poor form continued, Mourinho replied: "No."
Mourinho was speaking before United play Valencia in a Champions League group match on Tuesday.
"Every player is different, no player is the same," he said. "I see different actions but what you see is not really inside.
"I see upset people, some people that don't look like they lost a game.
"I see so-so but in the little two sessions of training we had [since Saturday] everything was normal, desire to work and play."
Mourinho added: "What I can do to improve things I do, and I will improve the things that depend on me and my work."
Has Mourinho spoken to Woodward?
United's 3-1 defeat by West Ham was their third loss in seven Premier League games, making it their worst start to a campaign since 1989-90.
Mourinho was asked if he had spoken to United's executive vice-chairman Ed Woodward since losing to the Hammers.
"That's a private matter," he said. "I'm not asking who you speak to. That's a private matter."
United midfielder Nemanja Matic played in the West Ham defeat, a display which defender Luke Shaw described as "horrendous" and "awful".
Matic added: "When you play for Manchester United everyone expects you win the games.
"When you don't win two games in a row, there is more attention on you - we know that.
"This game was really bad. I don't believe any player goes onto the pitch and doesn't try."
Speaking about Shaw's comments, Mourinho said: "He says 'we players are on the pitch, we have to perform, we have to give more'.
"I like that perspective but I don't agree totally. It is all of us, everybody in the club has a role to play.
"When we win we all win. When we lose we all lose. And when we lose it's the responsibility of everyone."
'I suspect Mourinho wants the sack'
Former Arsenal and England striker Ian Wright said the stream of negative stories concerning United were "embarrassing" for the club.
Wright told BBC Radio 5 live's Monday Night Club: "It seems to be on a daily basis. [Mourinho] talks about some players caring more than others, but doesn't name them - why mention that?
"Maybe he's trying to take the focus off the fact this is the biggest challenge of his career, to try to turn this around.
"This is embarrassing for Manchester United. What are the boardroom doing? How long is it going to carry on?"
Former Norwich and Blackburn forward Chris Sutton said it was "time for Mourinho to go".
"I suspect he wants the sack," said Sutton.
"He's an intelligent guy. Why would he want to keep carrying on and on by being provocative?"