Manchester United manager Jose Mourinho is hoping for the best after Marcus Rashford limped off with a knee injury.
The 19-year-old forward secured a 1-0 victory at Benfica after his free-kick caught out teenage goalkeeper Mile Svilar in Wednesday's Champions League encounter.
But shortly afterwards Rashford sat frustrated on the deck with a knee injury that forced him out of the Group A clash.
"Marcus Rashford, I thought was cramps because he was running so much that I thought it was about muscular fatigue," Mourinho said.
"But, no, he told me he was feeling something in his knee. It didn't look for me a big thing but you never know."
Phil Jones should return to fitness in Saturday's Premier League match at Huddersfield, but fellow centre-back Eric Bailly remains side-lined.
Marcos Rojo and Zlatan Ibrahimovic continue their comeback from serious knee ligament injuries, while midfielders Michael Carrick, Paul Pogba and Marouane Fellaini are currently out injured.