Tuanzebe is a regular in the reserve side at the Premier League giants, but Mourinho has suggested that it will not be long before he starts including the 19-year-old in his senior setup.
The 53-year-old told MUTV: "We lost Morgan Schneiderlin and Memphis Depay, two players who didn't play many minutes or many matches for us.
"They were two players from the squad, so we need numbers and probably Axel is one of the boys that's in the academy who is more close to playing with us.
"So we have brought him up to give him more experience, to make the first team more natural for him in case we need him to play in the upcoming matches and month, so he can be more adapted to us."
United are still involved in four competitions, meaning that they face the possibility of nine games before the end of February.