Richie Gray is a major doubt for Scotland's November internationals after Toulouse confirmed the second row will undergo back surgery.
Gray missed Scotland's tour to Singapore, Australia and Fiji in June due to the problem and the 27-year-old is unlikely to be available for Gregor Townsend until next year.
Scotland face three home Tests in November, starting with Samoa before hosting powerhouses New Zealand and Australia.
Gray's impending operation was confirmed by Toulouse coach Ugo Mola on Wednesday as the French club prepare for their opening Top 14 clash of the season against Oyonnax this weekend.
"Richie Gray trained earlier this week but he needs to be operated on for a back injury in the next few days," said Mola, who did not reveal how long the club expect Gray to be sidelined.
The forward's absence is not only a blow for Scotland but also for Toulouse as they prepare to begin the 2017-18 domestic season already without Peato Mauvaka and Julien Marchand.