Wales flanker Dan Lydiate will miss the Six Nations after a decision was made for him to undergo surgery on a bicep injury.
Lydiate was hurt during the Ospreys' Guinness PRO14 victory over the Dragons on New Year's Eve and going under the knife means he will be sidelined for the rest of the season.
— Ospreys (@ospreys) January 9, 2018
Ospreys medical performance manager Chris Towers said: "After speaking to consultants and seeking specialist opinion, the decision has been taken in Dan's best interests to undergo surgery.
"That process will take place this week, ruling him out of consideration for the rest of the current season."
Wales are already without Lydiate's fellow flanker Sam Warburton for the competition due to injury, while number eight Taulupe Faletau is recovering from knee trouble and thought unlikely to be back in action until late February or early March.
Gloucester back-row forward Ross Moriarty, however, is back to full fitness and could return to action this weekend.
The 23-year-old has been suffering with a nerve injury for much of the season but may be in line to face Agen in the European Rugby Challenge Cup on Friday.
Gloucester backs coach Tim Taylor told WalesOnline: "He's fit and training again and he will definitely be up for selection.
"It would be great to get him back involved over the next few weeks as well.
"He's fully fit now, he'll definitely get game time over the next four-week block."