The playmaker has started 11 of United's 12 fixtures in the top flight and Champions League this season, contributing four goals and five assists.
However, according to The Sun, the 27-year-old is not certain to start United's crucial encounter with their fierce rivals on Sunday.
The report claims that Fernandes was seen 'limping heavily' during a warm-down session on Thursday, the day after starring in the 3-2 victory over Atalanta BC.
Fernandes, who had been on the receiving end of a number of strong challenges from the Italians, will be assessed over the coming days.
United head into the game at Old Trafford sitting four points adrift of Liverpool in the Premier League table. body check tags ::