South Africa forward Rynhardt Elstadt will miss Toulouse's European Champions Cup game against Munster on Saturday because of Irish Government Covid-19 quarantine rules.
Elstadt, 31, returned to France on 19 March after returning home to undertake a pilot exam.
At that stage, competition rules would have allowed the South African to play in the Thomond Park game.
However, a two-week quarantine period is now required in Ireland.
"He (Elstadt) was in line with the rules. We gave him permission to go," said Toulouse coach Ugo Mola.
"The preparation for this clash has obviously been disturbed by Covid-19 protocols and our injuries."
Mola's men, joint-record four-time European champions, are also without nine backs due to fitness issues for Saturday's re-run of the 2008 final.
"It's one hell of a handicap when we know the intensity of a knockout match in the Champions Cup," added the Toulouse coach
The flank forward and lock's absence means he will be unable to face up against another South African-born forward CJ Stander.
Back rows CJ Stander, originally from the Western Cape, has won 51 caps for Ireland but will retire from rugby at the end of this season to return home to South Africa.
"CJ Stander's retirement is surprisingly early," added Mola.
"I regret that he will not be able to measure himself against his compatriot Rynhardt Elstadt."
The winner at Thomond Park will travel to the winner of the last-eight tie between Wasps and Clermont-Auvergne.