The 18-year-old limped off after 81 minutes, clutching his thigh, before heading straight down the tunnel.
Rashford, prior to his injury, was an unstoppable force for Man United, constantly hassling youngster Pablo Maffeo on the right hand side.
The exact severity of Rashford’s knock is yet to be determined, but Saturday’s Premier League game with Burnley could arrive too soon for the 18-year-old.
With Eric Bailly already set to be on the sidelines until 2017, Mourinho cannot afford to lose another fundamental aspect of his starting XI, and United fans will anxiously wait to hear the details of Rashford’s knock.
It ought to be noted that Rashford has started six out of United’s last seven games. For an 18-year-old, even one with seemingly superhuman capabilities, such an accumulation of minutes can have an adverse effect.
The likelihood – and by likelihood I mean my own completely arbitrary prediction – is that Rashford has picked up a thigh strain – a symptom of playing frequently over a short period of time. A short spell on the sidelines followed by a steady, patient period of recuperation will be required before supporters can see the youngster decimate left-backs again.