The England international came on as a substitute on 64 minutes at Old Trafford but was taken off 15 minutes later after picking up an apparent back injury, per Henry Winter at The Times:
Rashford was replaced by Jesse Lingard and walked straight down the tunnel, per Charlotte Duncker at the Manchester Evening News:
Rashford took to social media afterward:
The academy graduate has already had to contend with hip and groin injuries this season but may now face another spell on the sidelines.
Rashford, 22, has 19 goals in 31 appearances for the Red Devils this season, 14 of which have been scored in the Premier League.
Manager Ole Gunnar Solskjaer hasn't been helped by the fact Anthony Martial—his other senior choice in attack alongside Rashford—missed a chunk of playing time at the beginning of the campaign.
Solskjaer may call upon 18-year-old Mason Greenwood as his new option up front for the upcoming fixture against Liverpool. The youngster has impressed this season and has four Premier League goals in 2019-20.