MANCHESTER, England -- Jose Mourinho has said Manchester United forward Alexis Sanchez could be sidelined for "a long time."
The Chilean suffered a hamstring injury in training on Thursday and is likely to miss at least six weeks. He could miss as many as 10 games including Arsenal's visit to Old Trafford on Dec. 5 and the trip to Liverpool on Dec. 16.
The 29-year-old will undergo a scan to determine how serious the problem is but Mourinho is not optimistic.
"No scans yet but the player is experienced, the player knows what the injury is and also from the top of my experience, just the painful scream and the way the injury happened, I know it's going to be for a long time," Mourinho told a news conference on Friday. "It is not the little muscular injury that in one week or 10 days the player is ready.
"For me and also for Alexis, the feelings before the scans is that the grade is different than the [Victor] Lindelof one and the Lindelof one was not an easy one so Alexis has what I used to call an aggressive muscular injury."
United head to Southampton on Saturday seventh in the table, 14 points off the top and seven points adrift of the top four.
Mourinho's team have conceded five goals in the opening 15 minutes of games this season, a joint high with Fulham and Cardiff, and the Portuguese coach has asked for a fast start at St Mary's.
"I feel that in some matches the way we start is not that intense, emotional, aggressive way where I would like the team to start," Mourinho said. "Other times, like for example against Young Boys, we had that start and I can imagine what the game could be if after 10 minutes it's 2-0.
"Sometimes it is because of efficiency. Other times the way we approach the game and obviously it's a little confusing."
Marouane Fellaini was the hero against Young Boys on Tuesday after the Belgian scored a late winner to book United's place in the round of 16 of the Champions League.
He is set to be feature again against Southampton and Mourinho said the 31-year-old midfielder is finally getting the credit he deserves.
"Everybody knows Marouane is not [Diego] Maradona but everyone knows what Marouane is and what he can give," the United manager said. "In this moment, especially this season and last he did what strikers couldn't do which is score goals in important moments.
"I know him very well and I know the positions he can play; the jobs he can do. This season you saw him as a third central defender against Burnley and as a striker and as a number eight.
"He's very important in both boxes. Now people knows what Marouane is and he also feels that good feeling."