16 December, 2017
Bailly, so dominant in United's strong start to the campaign, has not played since the start of November after picking up an ankle injury while on global duty with the Ivory Coast.
Speaking to MUTV ahead of Sunday's trip to West Brom, Mourinho said: "He goes to surgery, the decision is made".
Sources told ESPN FC in September that Mourinho was unhappy with Mkhitaryan's contribution against United's top-six rivals, but the player appeared to have overcome his manager's reservations by making an impressive start to the season with two goals and five assists in all competitions.
United have eight more points after 17 games than they did at this stage last season, Mourinho's first in charge at old Trafford, but they lie second in the Premier League table - 11 points behind Pep Guardiola's record-breaking Manchester City.
Mourinho's team bounced back from their defeat to City with victory over Bournemouth at Old Trafford in midweek, but the 54-year-old rejected the idea it had been hard to lift the players after the derby. I know that he needs to grow. "I think Tony assembled a very good squad, lots of players of experience, physical players adapted to the Premier League with know-how, lots of experience".
"But I had that experience before in other clubs".
Clear Bay Area skies to offer great view of Geminid meteor shower
The Virtual Telescope said: "To make this meteor shower of particular fashion and very special this year is a nice coincidence". According to scientists, Geminids have a much slower speed than other meteors and typically come in at an angle in the sky.
"We go to clubs with a huge history where people look to the history and not to the moment and expectations are high".
"I've nothing to say in relation to that", said Mourinho.
That length of lay-off puts Bailly's hopes of taking part in February's Champions League tie with Sevilla in doubt and also brings the January transfer market into view.
"I'm not a big defender of the January market but there are players and situations that sometimes you have the chance to do and you shouldn't lose that chance", he said. "But if you can buy one you would buy in June for July, with the chance a few months before, then great".