Paul Pogba will miss Manchester United's Premier League match against Middlesbrough on Sunday and withdraw from the France squad due to the hamstring injury he suffered against Rostov.
United manager Jose Mourinho confirmed Pogba will be sidelined after having to be replaced two minutes into the second half of Thursday's Europa League victory over the Russians.
Mourinho's men won 1-0 on the night at Old Trafford to seal a 2-1 aggregate triumph in the last-16 tie, but saw the France midfielder limp off to be replaced by Marouane Fellaini.
The 24-year-old gestured to his leg and headed straight down the tunnel after sustaining the problem when pressing a Rostov player, applauding the home fans on his way off.
"Yes, hamstring," Mourinho said of Pogba's injury at his post-match media conference.
"I don't know for sure how long, but no Middlesbrough and no national team."
Pogba had been named in France's squad to face Luxembourg in World Cup qualifying and Spain in a high-profile friendly for next week's international break.
A goal from Juan Mata proved to be enough for United in a tense second leg, with Mourinho impressed by his side's battling qualities.
"Our plan was to kill the game when we had energy for that," he said.
"We tried to kill it in the first half, we hit the post, the keeper saved, we missed chances. Then they were trying, but my players fought hard.
"Rostov are a very difficult team to play against because they defend with a block of 10 players. It was difficult for everyone. Atletico Madrid, Bayern, Anderlecht, Ajax, Sparta Prague, Man United – everyone found it difficult to play against them.
"They are very organised, big discipline, and they can be dangerous on the counter-attack."