Arsenal defender Takehiro Tomiyasu will miss the rest of the season after having surgery on his right knee.
The 26-year-old has made only one appearance this season, as a substitute in a Premier League win over Southampton in October, because of the issue.
He initially sustained the injury in pre-season and had a surgical procedure in August, but required further surgery after problems with the knee persisted.
The Japan international has started his rehabilitation programme, which Arsenal said is expected to last until towards the end of this year.
“It has been the toughest period in my career for sure and it carries on a bit more but I won’t give up,” Tomiyasu posted on Instagram.
“Thank you for your support and see you soon at the stadium.”
Mikel Arteta’s side have suffered several key injuries this season, with forwards Kai Havertz and Gabriel Jesus ruled out for the rest of the campaign, while wingers Bukayo Saka and Gabriel Martinelli – and right-back Ben White – are also injured.
The Gunners are second in the Premier League, seven points behind leaders Liverpool, and next host West Ham at Emirates Stadium on Saturday.
BBC Sport