Manager Roberto Martinez withdrew the 29-year-old soon after and revealed at full time that he feared the worst, with ligament damage - and another lengthy spell on the sidelines - a real possibility.
A tweet from the Belgian FA's official Twitter account this afternoon has allayed those concerns, though, as Fellaini is only expected to miss the next fortnight.
"Fellaini out for a couple weeks and #BELCYP. Scan – left knee injury (MCL sprain). Get well soon Marouane!" the tweet read.
The former Everton ace will now miss his national side's clash against Cyprus in midweek, as well as United's meeting with Liverpool in the Premier League and the Champions League trip to Benfica on October 18.