Nagusa was hurt in the act of scoring his side's fourth try in a 41-3 victory over Racing, which moved Montpellier eight points clear of its opponent at the top of the table.

As Nagusa stretched to dot the ball down over the line, an opponent landed on his left leg. The Fiji wing was withdrawn immediately and reportedly left the ground on crutches.

The injury soured an otherwise outstanding day for Montpellier, which claimed further tries through Jan Serfontein (2), Nico Janse van Rensburg and Louis Picamoles in a hugely convincing win.

Vern Cotter's side remains unbeaten in home league matches this season.

Elsewhere, rock-bottom Oyonnax boosted its survival hopes with a 26-20 win at Bordeaux-Begles that owed much to two tries in the first 17 minutes.

Chris Ashton scored a hat-trick as Toulon thumped Agen 54-5 to give Oyonnax a further lift, while Pau edged out La Rochelle 18-15 and Clermont Auvergne edged past Brive 11-9.