Glasgow Warriors lock Al Kellock will miss Scotland's entire Six Nations campaign after being ruled out for up to four months following arm surgery.
The 32-year-old former captain, who has 56 caps, expressed his disappointment on his Twitter account.
"Gutted about the arm but part of the job. I've had a good run for the last few years - back soon enough," he said.
Glasgow head coach Gregor Townsend said Kellock would be disappointed to miss the 1872 Cup against Edinburgh.
Townsend added: "He has played a prominent role in these games over the last few season and thrives against Edinburgh.
"We wish him well in his recovery and he still has a big role to play at the club as he works his way back to full fitness."
Meanwhile, X-rays have shown that Glasgow centre Mark Bennett has a fractured toe but will not require surgery.
Warriors say Bennett, who suffered the injury on Scotland Sevens duty, will be out for "several weeks".