Top 14 strugglers Bayonne's battle to avoid relegation suffered a blow as Fijian international centre Gabiriele Lovobalavu was ruled out of the rest of the campaign because of a knee injury.
The 28-year-old - who has scored two tries in his 11 appearances this season - suffered a badly twisted right knee in the early stages of last Saturday's Top 14 18-8 defeat by Racing-Metro.
The medical staff said that he would be out for at least four months and will undergo an operation in the coming days.
It is the second time that the former Toulon player has injured his knee this season, he tore ligaments in his left knee in the home match with Racing-Metro last September.
Bayonne are presently third from bottom of the Top 14, four points ahead of Oyonnax, although the latter have two games in hand on them.
Bayonne's fellow Basque side Biarritz look certain to be one of the two that go down as they are bottom, 17 points adrift of Oyonnax.