Paul Pogba needs "conservative treatment" on a foot problem and will not travel to Alkmaar for Europa League duty this week.
Paul Pogba will miss Manchester United's Europa League clash with AZ on Thursday as he requires further treatment to a foot injury.
The France international sustained the problem in the 1-1 draw with Southampton in August and only returned to action in last Wednesday's EFL Cup match with Rochdale.
Pogba then played in Monday's 1-1 Premier League draw with Arsenal at Old Trafford but will not travel with the rest of the United squad to Alkmaar.
"Following a specialist's opinion, Paul Pogba requires a period of further rest and conservative treatment for the foot injury he sustained during the game against Southampton in August. Updates will follow in due course," United said in a statement.
Aaron Wan-Bissaka, Phil Jones and Anthony Martial also remain out of action, as does left-back Luke Shaw, who has not played since the 2-1 home defeat to Crystal Palace in August.
Diogo Dalot and Angel Gomes return after injury lay-offs, while manager Ole Gunnar Solskjaer has also called up Brandon Williams, who made his debut against Rochdale, and James Garner.
There are 10 academy graduates in total in United's 21-man group.
The Red Devils beat Astana 1-0 on matchday one, while AZ, who are third in the Eredivisie, drew 2-2 away to Partizan.