Ander Herrera suffered a hamstring injury just 17 minutes into Manchester United's 0-0 draw in the first-leg of the Champions League last 16 clash against Sevilla on Wednesday (21 February).
Jose Mourinho confirmed after the game that it is a recurrence of the same injury that saw him miss the last three games prior to their clash against the La Liga outfit.
Herrera missed United's Premier League outings against Newcastle United and Huddersfield Town and was also absent for the FA Cup tie against the Terriers on Saturday (17 February). The Spanish midfielder was passed fit ahead of the FA Cup game but the manager chose not to risk him and give him more time to work on his fitness.
The 28-year-old is likely to be sidelined for a few weeks after the Portuguese manager suspected that it was a "bad injury" following the game. The manager was impressed with his contribution when he was on the pitch admitting that he showed no signs of the injury until he went down after attempting a back heel pass in the opposition box.
"I think it's a bad injury," Mourinho said during his post-match press conference, as quoted on United's official site. "The medical department gave [pronounced] him fully fit on Saturday. He trained on Saturday, Sunday and Monday and looked fit."
"The way he was playing during the time he was on the pitch, he showed the intensity that is only possible when you are fit. He pressed a lot, really high; we started the match not giving one inch to [Ever] Banega.
"Then it was a backheel that created a contraction in the muscular area where he had the previous problem," the Portuguese coach explained.
Herrera was replaced by Paul Pogba, who started on the bench, with Scott McTominay preferred over the France international. The Spaniard's injury will leave Mourinho slightly short in midfield ahead of their game against Chelsea on Sunday (25 February).
Pogba and Nemanja Matic will be expected to start when the Blues visit Old Trafford with one of Michael Carrick or McTominay partnering the duo. Chelsea, who are currently in fourth on the Premier League table, can go level on points with the second placed Red Devils with a win.