Juventus did not elaborate in its statement to The Associated Press amid reports the midfielder arrived late for a team retreat Wednesday night.
The Serie A side won the first leg of their round-of-16 matchup 1-0, but they got potential bad news when Federico Chiesa, who had just returned from injury, limped off in the second half.
The 29-year-old Pogba had also only just returned to action, making two appearances for Juventus following a long injury layoff.
Juve boss Max Allegri said they will have to wait for scans to determine the extent of Chiesa's injury, but said France midfielder Pogba would be available again from Friday.
"There are rules within a team like Juventus, and they need to be respected above all by the veterans," Allegri said when asked about Pogba. "To go all the way in a competition, you need as well as technique and quality, more importantly, character and moral strength."
Pogba, a key playmaker in France's World Cup title run in 2018, ended up watching from the stands as Juventus won on an Angel Di Maria goal.
It is not the first time Pogba has been in trouble with club management. At United, he had a complicated relationship with former coach José Mourinho.