Manchester United defender Matthijs de Ligt and Joshua Zirkzee were both absent from Wednesday's training session.
Michael Carrick is currently preparing for his second game as Man United interim boss after starting his tenure with an impressive 2-0 victory in Saturday's derby clash against Manchester City.
Carrick's charges will travel to the Emirates Stadium for Sunday's meeting with Premier League leaders Arsenal.
Preparations for that tough encounter continued in training on Wednesday, although De Ligt and Zirkzee were notable absentees from the session at Carrington.
De Ligt, Zirkzee miss Man Utd training
De Ligt has already missed the last 10 competitive matches with a back problem, and his absence from Wednesday's session suggests a return to action is not imminent.
As for Zirkzee, he was left out of the Manchester derby squad due to a knock and is seemingly in a race against time to
While De Ligt and Zirkzee were absent from the training session, 18-year-old Shea Lacey was once again involved with the senior squad.
The teenager made two substitute appearances against Burnley and Brighton & Hove Albion earlier this month, but was sent off against the latter for two bookable offences.
Lacey's dismissal in the FA Cup third-round defeat forced him to miss the Manchester derby through suspension.
The highly-rated youngster is now available for selection and will be hoping to make the squad for Sunday's clash with the Gunners.
What about Mazraoui?
Noussair Mazraoui, meanwhile, could feature in Sunday's squad despite being given some extra time off following Morocco's dramatic defeat to Senegal in the Africa Cup of Nations final.
The 28-year-old has played plenty of football in the last month after starting each of Morocco's seven matches at the tournament.
Carrick is expected to provide a clearer picture on Mazraoui's availability when he speaks to the media in Friday's pre-match press conference.