Arsenal are set to be without Danny Welbeck for some time.
The English striker picked up a serious ankle injury in the 0-0 draw with Sporting Lisbon and could miss the rest of the season.
Unai Emery said after the game: “We think it’s a serious injury.
“Every injury is different. He broke something in his ankle and it’s a different injury than another.
“Now he’s at the hospital and the news is at the moment we are going to wait, but we think this is a serious injury.”
It will be a big blow to Arsenal after Welbeck's impressive start to the season, with the former Manchester United man particularly excelling in the Europa League.
The Gunners do have Pierre-Emerick Aubameyang and Alexandre Lacazette as their forward options, with Eddie Nketiah set to get more game time now.
And Welbeck's injury is set to force Arsenal to act in the January transfer market, with Emery and Sven Mislintat stepping up their interest in a £45m target.
According to The Sun, the Gunners will look to sign exciting Lille winger Nicolas Pepe, who they were planning on targeting in the summer.
The French-born Ivorian forward has been in sensational form for Ligue 1's second-place side.
The 23-year-old has eight goals and five assists in 13 league games.
Pepe has been linked with various big clubs across Europe and recently spoke about the rumours linking him with a Lille exit.
He said: “A preference between Dortmund, Bayern or Arsenal? They’re all big clubs, I was not aware of these rumours, although it’s nice.
“Leave Lille at the end of the season? We do not even know what I’ll be doing tomorrow!”
Pepe would likely be the man to slot in on the right-hand side of Arsenal's attack, with Henrikh Mkhitaryan and Alex Iwobi failing to sparkle in the role.