Lyon president Jean-Michel Aulas has publicly castigated defender Milan Bisevac after the experienced centre-back's "unforgiveable" attitude proved a major factor in Sunday's damaging defeat at Reims.
OL's title challenge was ended and their chances of qualifying for next season's Champions League seriously compromised as they lost 1-0 in the Champagne region.
It was a third successive Ligue 1 reverse in a five-game winless run for the seven-time champions, and meant arch-rivals Saint-Etienne leapfrogged them into the top three.
Aulas quickly accused Serbia international Bisevac, 29, of provoking his team's latest setback as, having conceded the early second-half penalty which the struggling hosts scored to secure a welcome victory, the former Valenciennes and Paris Saint-Germain player reportedly told referee Olivier Thual "I must say you're a bit of a t***" and was promptly dismissed.
"What's unforgivable is to go and compromise the balance of the team and get sent off due to a lack of self-control, because once the penalty's been given, it's been given," Aulas, 64, told L'Equipe.
"For an experienced player, it's a 'sackable offence' which must not be pardoned. Milan must think about the consequences for the squad and the club."