Jose Mourinho fears Marouane Fellaini has suffered a "bad" back injury, but maintains the Manchester United midfielder will still join up with the Belgium squad during next week's international break.
Fellaini completed the entire match as substitute Marcus Rashford gave United a stoppage-time 1-0 win at Hull City to maintain their 100 per cent start to the Premier League season under Mourinho.
But an apparent setback for the 28-year-old midfielder took some of the shine off a hard-fought triumph, with boss Mourinho praising the performance of a player who has rarely enjoyed a high standing with United's supporters.
"I saw the way Fellaini and the two central defenders controlled everything long, high and short," Mourinho told a post-match news conference.
"But I can't play Fellaini for some time. He has a muscle injury in his back. He will fly [with Belgium] but it is bad."
Mourinho was happy to see his team battle to a gruelling win on the back of far more straightforward encounters versus Bournemouth and Southampton, and revealed he was forced to put the breaks on a hungry squad earlier this week.
"I was telling them at half-time that on Wednesday on the training ground they were most intense than on the pitch in the first half today," he explained.
"I had to stop the session. We have a long way to go, we have a lot to improve. We will have ups and downs."