Mikel Arteta has said that the injury that caused Gabriel Jesus to depart Arsenal's FA Cup third-round defeat against Manchester United on a stretcher is "not looking good."
The Arsenal forward left the pitch in the 40th minute with the match goalless in north London following an innocuous coming together with United captain Bruno Fernandes.
Jesus clipped Fernandes just outside Arsenal's 18-yard box, causing Fernandes' boot to come loose.
The United midfielder then twice threw his boot to the ground in frustration at referee Andrew Madley deciding against rewarding a free kick, earning him a booking for dissent. While Fernandes fumed, Jesus stayed down and required a stretcher.
United later took the lead through Fernandes on 52 minutes before Diogo Dalot was dismissed for a second yellow card after fouling Mikel Merino. Gabriel Magalhães equalised for the hosts soon afterwards before United eventually progressed to the fourth round on penalties.
Asked about Jesus' injury after the match, Arteta told a news conference: "Big worry, that's my feeling. He had to come off on a stretcher with a lot of pain, touching his knee. It's not looking good."
The Arsenal boss confirmed the injury was affecting the opposite knee to the one in which he suffered an ACL injury in 2022.
"The worrying factor is the feeling that he had. When he had to come off and the pain that he was in," Arteta said.
Jesus' worrying-looking injury is the latest suffered by one of Arsenal's stars.
Bukayo Saka is ruled out until March after he required surgery on a hamstring injury, while Arsenal are also without Ethan Nwaneri (muscle injury), Takehiro Tomiyasu (knee) and Ben White (knee).
Information from ESPN'S James Olley contributed to this report