Romelu Lukaku is unlikely to face Juventus in the Champions League after missing training for Manchester United on Tuesday.
United head to Turin for a Group H meeting on Wednesday, having been beaten 1-0 at home by Massimiliano Allegri's side two weeks ago.
Lukaku started that match but was benched for United's following game, a Premier League win against his former club Everton.
And the Belgium striker was not included in Jose Mourinho's squad for United's weekend victory away to Bournemouth, secured by Marcus Rashford's late goal.
Mourinho confirmed after a 2-1 win at the Vitality Stadium that Lukaku sustained a muscle problem in training and needed time to recover.
But the 25-year-old, who has not scored for United since the middle of September, was unable to take part in Tuesday's session.
Lukaku's absence could offer England striker Rashford a chance to shine, with Mourinho's other attacking options including Alexis Sanchez and the in-form Anthony Martial, who has scored in four successive Premier League games.
Juventus will be through to the next round if they avoid defeat against United, while the Serie A champions will guarantee they top the group if they win.
Allegri has injury problems of his own, though, with doubts over Douglas Costa, Mario Mandzukic, Giorgio Chiellini, Federico Bernardeschi and Blaise Matuidi.
