Mourinho told reporters ahead of kick-off that Bailly had suffered an injury during the international break.
“I don’t think we have many options,” Mourinho said. “Bailly [was] injured in the national team.”
Rashford played in both of England’s games, but despite a knock, was on the substitutes bench for United at Anfield, unlike Bailly and Fellaini who missed the matchday squad entirely.
Mourinho didn’t reveal whether Bailly would be back in contention for United’s third UEFA Champions League group stage game, against Benfica this Wednesday.
Victor Lindelöf is another option, and Mourinho is willing to use his £30.7m summer signing in European games more so than in domestic fixtures, due to the different style of play.
United missed Bailly’s presence against Liverpool, with the combination of Jones-Smalling failing to impress. Jones, though a key contributor this season when playing alongside Bailly, looks a far worse player without his regular partner.
Smalling, for his part, is simply a lesser player than Bailly. United were fortunate that Sadio Mane was unavailable for Liverpool, the visitors wouldn’t have been able to cope with the former-Southampton man without Bailly.