England backrower Sam Simmonds will be sidelined for the next six to nine months after tearing his anterior cruciate ligament while playing for Exeter Chiefs on Saturday, casting doubt over his chances of playing at next year's Rugby World Cup in Japan.
The No. 8 could return for the last few weeks of the season but will miss the upcoming November internationals and the Six Nations, which starts in February, his club said.
"We'd like to hope we can maybe see him before the end of the season but it's going to be touch and go," Exeter director of rugby Rob Baxter said. "Obviously he is upset. He was looking forward to having a big season."
Simmonds, 23, has scored five tries this season to help Exeter win all five of their Premiership matches so far. They are in second place, a point behind Saracens.
The Chiefs were also hit with the news that lock Jonny Hill will be facing a spell on the sidelines. Hill, who toured with England in South Africa this summer but is yet to win his first cap, sustained a ligament injury to his hand and will also be out for a number of weeks.
Next year's Rugby World Cup starts on Sept. 20.