Marouane Fellaini was forced with a fresh injury while playing for Belgium in a World Cup qualifier against Bosnia and Herzegovina – handing Manchester United boss Jose Mourinho another injury concern ahead of a crucial trip to Liverpool.
Fellaini sat out of training with his national team this week, still feeling the effects of an Achilles injury picked up following a nasty challenge from Southampton's Shane Long on 23 September.
The former Everton midfielder missed last week's Champions League win over CSKA Moscow with that knock, but returned to the starting XI against Palace, scoring twice in that 4-0 win just before the international break.
While his club and country teammate Romelu Lukaku wasn't risked, Fellaini was cleared to play by Belgium boss Roberto Martinez and was named in the starting XI for Saturday evening's penultimate qualifier against Bosnia and Herzegovina.
But after just 29 minutes, the powerful midfielder went down with what appeared to be a knee injury, with Anderlecht's Leander Dendoncker immediately brought onto replace him.
Even a minor problem could mean Fellaini is a doubt for the trip to Anfield on Saturday 14 October with Mourinho already short on numbers in the middle of the park.
United are yet to set a timeframe for Paul Pogba's return, with his manager classifying his hamstring problem as a "long-term problem."
Michael Carrick has also been unavailable for his side's last time games through injury, with Nemanja Matic, who has played every minute of the Premier League campaign so far, and Ander Herrera Mourinho's only other options.
United may also have some concerns over star striker Lukaku. The 24-year-old underwent an MRI scan following an injury scare in the build-up to United's 4-0 win over Crystal Palace in their final match before the October international break. The Royal Belgian Football Association (KBVB) revealed earlier this week the scan had found no signs of a fracture and would place the striker on an individual training programme to ease any concerns, but decided anyway not to select him for tonight's clash against Bosnia.
Martinez may call upon his player for Tuesday's final group game against Cyprus.