England midfielder Ross Barkey scored twice with on-loan Arsenal forward Nicolas Pepe also getting two goals as Nice thrashed Montpellier in Ligue 1.
Pepe got the first in the 15th minute and Kephren Thuram-Ulien made it 2-0.
Wales international Aaron Ramsey set up Pepe for the third and Andy Delort added a fourth before Teji Savanier pulled one back for the visitors.
But Barkley, on as a 67th-minute substitute, scored twice in the last eight minutes as Nice won 6-1.
Barkley, 29, has played 33 times for England but left Chelsea in August before signing for Nice on a free transfer a few days later.
It was Nice's first match since they lost 1-0 on Sunday to third-tier side Le Puy Foot 43 in the last 64 of the French Cup.