Scotland captain Greig Laidlaw will miss the autumn after suffering a fractured leg during Clermont Auvergne's European Champions Cup win at Ospreys on Sunday.
The Clermont scrum-half has been ruled out for up to 12 weeks as a result of a break he sustained after coming off the bench in a 26-21 victory at the Liberty Stadium.
Laidlaw faces a battle to return this year and will definitely sit out Scotland's Tests against Samoa, New Zealand and Australia next month.
Top 14 club Clermont revealed that the playmaker will not require surgery.
Laidlaw's participation in the Six Nations was cut short when he damaged ankle ligaments against France in February, but he should be fit for the start of the 2018 tournament.
John Barclays, who stepped in to skipper Scotland in British and Irish Lion Laidlaw's absence, is also a doubt for the November Tests as he has been suffering from concussion.