Arsenal have confirmed that left-back Kieran Tierney faces between four to six weeks on the sidelines.
The left-back hobbled off in the first-half in the defeat to Liverpool on Saturday evening.
The Gunners have said that the Scot does not require surgery, but is now expected to miss the vast majority of the rest of the season, if not all of it.
Arsenal face Sheffield United in between the two European games before they host Fulham on April 18.
Cedric Soares is poised to replace Tierney at left-back, although Bukayo Saka is also an option for Mikel Arteta.
The youngster missed the Liverpool reverse but he and Emile Smith Rowe could both return on Thursday.
Arteta will be seeking a response following their 3-0 drubbing on Saturday which ranks among their worst performances of the season.
Gary Neville was particularly scathing in his assessment of the Gunners as he singled out the role of their forwards.
He said on Sky Sports : "The shape under Mikel Arteta has been really good. The back four pushes up to a really good line. They have a compact 30 or 35 meters between them.
"That wasn't too different on Saturday but what was really different was the effort - or lack of it - of that front six.
"Odegaard did try and put a little bit of a press on but he was on his own. The rest of them, I'd go as far as to say they were a joke.
"At half-time, you start to start to question yourself a bit because you think, 'it's Liverpool, they're a good team, it's 0-0 and they're still in the game'.
"But I think Arteta will have been shocked by the lack of application he saw against the ball in the front part of his team.
"Liverpool just won the ball back time and time again and it was a walk in the park for them. They had no pressure against them. It was embarrassing."
