Mainoo's injury was one part of a damaging few days for United, who also saw Amad Diallo ruled out for the season, Manuel Ugarte suffer a knock and both Christian Eriksen and Leny Yoro come down with illness.
The 19-year-old has emerged as a key player at United over the past year and his absence, along with a host of other fitness concerns, left ageing Casemiro as the only recognised fit central midfielder for the defeat at Tottenham.
It had been reported earlier this week that Mainoo hopes to return for United following the international break in March, ruling him out for eight games in total.
Asked how training has gone this week, the United boss told reporters: "We didn't lose players, we recover players.
Ruben Amorim remains unsure when Kobbie Mainoo will be able to play for Manchester United again.
