Scotland number eight Simon Taylor has suffered a serious knee injury that will force him to miss the summer tour to South Africa.
The 26-year-old, whose career has been blighted by injury, has been told he will be out of action for at least four months after a scan revealed significant damage to his knee.
Taylor, who has been selected for the last two Lions tours only to be forced home early because of injuries, suffered his latest setback playing for Edinburgh in Friday's 22-16 Celtic League win over Connacht.
He will undergo surgery on his medial ligament next week, although the scan and subsequent examination showed no significant injury to his previously reconstructed cruciate ligament.
Taylor will begin rehabilitation with the Gunners' medical staff.
Scotland coach Frank Hadden described the loss of Taylor as 'tough news'.
He said: "Clearly it's a blow to lose Simon from our tour to South Africa.
"It's tough news for him as he has worked so hard to regain his fitness and form after the injury which caused his premature departure from last year's Lions tour.
"During the Six Nations Championship he was beginning to look like his old self again. I wish him a speedy recovery."
Taylor, who won his 46th cap in Scotland's victory over Italy in March, was philosophical about his latest injury.
He said: "It sounds like I'll be spending a bit of time taking it easy before immersing myself in the rehabilitation programme.
"It (the injury) is just part of life. It's not the end of the world."