Paul Pogba has handed Manchester United an injury scare before the Etihad derby after the France midfielder missed training on Friday.
Pogba worked on his own indoors at Carrington after sustaining what was described as "a little injury", raising concerns that he could be a doubt for the clash with Manchester City on Sunday.
United are already waiting to see if Romelu Lukaku will be fit after the Belgium striker returned to full training on Friday having missed the last two games with a hamstring injury.
Both Lukaku and Pogba have another session to prove their fitness on Saturday but manager Jose Mourinho will not want to be without two of his biggest stars for one of the most eagerly-anticipated games of the season.
Earlier, Mourinho insisted there were no major injury problems following the midweek win over Juventus after Alexis Sanchez shook off the effects of a dead leg to take part in training.
"From Juventus, we don't bring important injuries," said the United boss. "We have 'touches' but I don't think any player that was available for Juventus will be out.
"We have a chance that Lukaku could be back. He is training with the team this morning. If this answer is positive and we have, of course, one more session tomorrow, he's ready."
United recovered from two goals down to win the Etihad derby 3-2 in stunning fashion in April, and have continued that trait this season with comeback wins over Juventus, Newcastle and Bournemouth.
But Mourinho has warned his players to "grow up" and stop conceding first to their opponents, wary that unbeaten City are unlikely to let their rivals off the hook so easily again.
Asked if he is happy with his players' character to keep fighting back, the United boss said: 'We can go to the other side: why we always concede before the opponent.
"In a positive way, it's easy to feel that we are not a team that gives up and we always find a way to fight back -– sometimes changing results and sometimes not.
"We are a team that has that collective spirit to fight back, but it's not always possible.
"If we keep conceding goals before the opponent, there will be a day where we cannot come back, so we have to grow up in our approach.
"It's clear the team is growing up, but we have to grow up in our compactness and start matches well."