Toulon boss Bernard Laporte has admitted that the club failed in their efforts to replace Carl Hayman this season.
Former All Blacks prop Hayman hung up his boots at the end of last season after playing a major role in the club's three European Cups and one Top 14 title.
To replace him Toulon signed Northampton's Salesi Ma'afu along with former England prop Matt Stevens, but neither move has worked out.
Ma'afu was released by the club following his convinction for assault earlier this year, while Stevens has been ruled out on medical grounds.
That has left Toulon relying on Fiji's Manusa Saulo, who noticeably struggled in the side's defeat to Toulouse last weekend. Laporte believes that disruption has played a major role in their problems this season.
"We've lost our efficency. We got our recruitment wrong," Laporte told Rugbyrama.
"We took two tighthead props to replace Hayman, and the two of them aren't available. Ma'afu had to leave and Stevens has been forced to stop rugby on medical grounds. Honestly losing them both is a lot.
"Also our second row has never fully taken shape. After we lost Ali Williams and Bakkies Botha we recruited Samu Manoa and Paul O'Connell (who retired), but we've had to do without them.
"We've lost the calmness from before. With those guys who gave us that tranquility, we did more."