Arsenal defender Hector Bellerin will miss the remainder of the season after scans confirmed he has suffered an anterior cruciate ligament rupture, the club have said.
Bellerin was taken off on a stretcher after 72 minutes of his side's 2-0 victory over Chelsea and will be out of action for the next six-to-nine months.
"Further to the injury sustained during our match against Chelsea on Saturday, we can confirm that Hector has ruptured the anterior cruciate ligament of his left knee," an Arsenal statement read. "Hector will undergo surgery to repair this in the coming days.
"The rehabilitation process is expected to take between six-to-nine months and therefore rules Hector out of action for the remainder of this season.
"Everyone at the club will now be working as hard as we can to ensure Hector is back on the pitch as soon as possible next season."
Arsenal manager Unai Emery said he had players to fill in for Bellerin and was unlikely to dip into the transfer market to sign a replacement, having previously said he could only take players on loan in the January transfer window.
"We have Ainsley [Maitland-Niles]." Emery said. "He can help us by playing like a right back or a right winger.
"And also, [Stephan] Lichtsteiner is another player. I don't forget [Carl] Jenkinson -- he played some matches and if we need [him], he is OK to help us."
Arsenal are fifth in the Premier League table -- three points behind Chelsea in fourth -- and host Manchester United in an FA Cup fourth round tie on Friday.