Bruno Fernandes is facing a race against time in order to be available for Manchester United’s round-of-16 second-leg with Atletico Madrid on Tuesday.
The Portuguese international has tested positive for Covid-19 and missed Saturday’s dramatic win over Tottenham as a result.
In his absence, Paul Pogba was pushed further up the field against Spurs with the Frenchman, Jadon Sancho and Cristiano Ronaldo combining effectively.
Anthony Elanga scored what could be a crucial goal in the Spanish capital last month, latching onto to a Fernandes pass as United rescued a result after a game in which they had largely been outplayed.
There is a hope Scott McTominay will be fit after missing the Spurs win with a calf injury, while Luke Shaw was due back in training on Monday following a recent positive Covid test of his own.
David de Gea, meanwhile, is thought to have given a false positive prior to Saturday’s win so could feature.
"With Scotty, I hope (he is fit) but he had some muscular problems with his calf," Rangnick said. "That’s why we decided not to play him (against Spurs), because Scotty is only valuable if he can perform with 100% of his physical capacity.
"Luke hopefully will be back in training Monday and Bruno we will have to wait and see until Tuesday. This will probably be a last-minute race with him - due to COVID-19.
"We have to be careful with COVID-19 tests. David (de Gea) was the same. David yesterday was out, he was not supposed to play but then it turned out that his first fast test was false."
