Arsenal head coach Mikel Arteta has admitted Kieran Tierney's injury will force the Gunners to "move a lot of pieces" in search of cover.
The Gunners have confirmed that the left-back has suffered knee ligament damage and will be out between four and six weeks.
Without a clear option to replace the Scotland international, Arteta said he will be forced to get creative as his side look to finish the season strong.
What was said?
"Yes, we're going to have to make some adjustments because his qualities are unique and we don't have anybody with his qualities within the squad unless we start to move a lot of pieces," said the Gunners boss.
"Without any time to train, it is a little bit dangerous to do, but we're going to have to find different ways to fill that gap and use other things that can be as effective as well. That's the reality. You have to change something and you have to find a different way of attacking.
"At the same time, the structure when you are defending and in transitional moments has to be stable and has to be done by players that are comfortable doing that."
Who could replace Tierney?
The two most likely options to replace Tierney are Bukayo Saka and Cedric Soares, but neither is an obvious choice.
Saka has played left-back for Arsenal but has excelled in a more advanced role this season, while Soares is a natural right-sided player.
What games will Tierney miss?
Tierney will miss both legs of Arsenal's Europa League quarter-final clash with Slavia Prague, and will likely miss Premier League matches with Sheffield United, Fulham, Everton and Newcastle at the least.
Should Arsenal reach the Europa League semi-final, where they'd face either Villarreal or Dinamo Zagreb, Tierney would have an outside chance of being fit for the second leg on May 6.
A more likely target would be the final on May 26, as well as the rescheduled Euro 2020 tournament which is scheduled to kick off in June.