Marouane Fellaini suffered an injury less than a minute into his appearance from the bench against Tottenham Hotspur on Wednesday night.
The Belgian, who spent all of December sidelined with a knee problem, came on to replace Paul Pogba at Wembley in the second half.
But he was, much to the confusion of all watching, hooked off for Ander Herrera just eight minutes later despite showing no signs of discomfort and went straight down the tunnel.
However, this video clearly shows Fellaini, 30 seconds after coming on, picking up what looks to be a strained or pulled muscle after competing for a loose ball.
Jose Mourinho finally lost his temper midway through the second half, his side once again cut open by an effervescent Spurs side, and many interpreted his hooking of Fellaini as a symptom of his growing chagrin.
But it turns out that anger was instead related to the notion that, once again, Mourinho was set to be short of options in midfield. Another injury in the same position could suddenly cause real problems.
Fellaini’s superb patch of form in September feels like eons ago now. The 30-year-old, with speculation surrounding his future refusing to die down, has continued to pick up niggles preventing him from breaching the starting XI, and you wonder whether that will factor in the club’s stance on offering him a new contract over the next few months.