Toulon - South African back-row forward Juan Smith will miss Toulon's crucial Top 14 clash with Montpellier on Sunday, the club said on Thursday.
The 34-year-old has a heel injury but Toulon believe he may be fit even by next weekend and the final match of the regular season.
"Smith is suffering from plantar fasciitis," said a team statement.
"If it's established that he won't play against Montpellier... he's undergoing daily treatment to regain fitness as soon as possible to try to be available for the next matches."
Toulon and Montpellier are level on points in second and third with two games of the regular season remaining.
Only the top two receive a bye in the first round of the play-offs straight into the semi-finals.
With Clermont almost certain to finish top, Toulon could secure second place with a bonus point victory, although second place, for which Racing 92 also remain in the running, will likely be decided on the final day of the regular season.