Kieran Tierney injury means Arsenal must either change way they attack or alter their system completely

Kieran Tierney is facing a fight to be fully fit for this summer’s European Championships after being ruled out for at least a month, if not longer, with a knee injury.

Tierney, a key player for Arsenal and Scotland, limped out of Saturday’s match against Liverpool after sustaining ligament damage to his left knee.

Arsenal manager Mikel Arteta said he did not know whether Tierney would be able to play again this season and added that his prospects for the Euros depend on how the injury “evolves” in the coming weeks.

“It could have been worse because the action looked quite scary,” said Arteta, ahead of Thursday’s Europa League quarter-final against Slavia Prague. “But he is feeling better and the damage is not that bad. At the end of the day, it is maybe not the bad news we were expecting after the game.

“We are going to have to go day by day to see how Kieran is feeling, how he is reacting. When we get close to playing time, depending where we are how he is feeling, we will make a decision.”

Tierney’s absence is likely to mean Cedric Soares fills in at left-back, although it could also result in Bukayo Saka returning to a more defensive position.

Meanwhile, Brazilian forward Willian has urged more players to speak out about racial abuse and has demanded greater action from authorities to deal with the issue.

“We as players cannot do a lot,” said Willian. “We do what we can do, we report it, we share it with you guys [the media] and we speak about that, but we want action. We don’t see any action from the authorities in that case.

“The advice [to other players] is to share. To put it on their social media, to speak, to never have fear to speak about that. These people have to pay for that. I don’t know why they do that, I want to know. We have to speak, we have to share on social media.

“I was in that situation one month ago, and it was very difficult for me because I have a lot of things on my phone and I saw a lot of horrible words against my family, for example. After that, I said to myself, ‘enough is enough, I have to try something’ - to take action against racism and online abuse.”

ANALYSIS: How Arsenal might fill the Tierney void

There is no hiding from the fact that Tierney’s knee injury is a significant blow for Arsenal and, potentially, for Scotland. Tierney has emerged as one of Arsenal’s most important players this season, often providing a defensive resilience and offensive edge that they have otherwise lacked.

In his absence, the likelihood is that Cedric Soares will take his place at left-back. Cedric is right-footed, though, and therefore offers none of the overlapping threat that Tierney provides on the flank.

Arsenal will therefore have to either change the way they attack or alter their system completely. A return to a back three is a possibility, with Bukayo Saka playing as a left wing-back, or the teenager could even be moved back into a more defensive position.

There is no easy solution here. By moving Saka, Arsenal will reduce the attacking threat posed by arguably their most dynamic forward. By playing Cedric at left-back, they will lose the width that allows them to stretch opposition defences.

Mikel Arteta hinted that a change of shape is unlikely for the moment, primarily because there is so little time to work on a new formation in training. But he knows better than anyone that something has to change.

“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 Arteta. “Without any time to train, it is a little bit dangerous to do. But we're going to have to find different ways to fulfil that gap and use other things that can be as effective as well.

“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.”

Arsenal had looked for a backup left-back in January, after loaning Sead Kolasinac to Schalke, but were ultimately unable to sign anyone in that role. Of all the positions in their squad, left-back was perhaps the one area where they did not want to lose their main man. Tierney’s injury is a major problem for Arsenal, and their reaction to this setback could define the rest of their season.