Nice were winless in their last three in the league as their strong start to the season stuttered, but they converted the first chance of the match to take the lead when Germain drilled a low shot past Steve Mandanda from 20 yards.
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In contrast, Marseille had won their last three matches in all competitions and they had a chance to equalise midway through the first half when top scorer Michy Batshuayi could not turn Benjamin Mendy's cross home from close range.
Hatem Ben Arfa received his first call-up to the France squad in four years this week and he looked to show just why when he created an opening for himself on the half-hour mark when he beat Karim Rekik, but his curling effort was fielded with relative ease by Mandanda.
Batshuayi tested Mouez Hassan from long range and saw his effort from a tight angle blocked as Marseille went in search of the equaliser after the restart, but Nice's defending was stubborn and the home side were increasingly limited to speculative efforts as the game entered the final 20 minutes.
Mendy and Bouna Sarr fired wide from promising positions, and though Said Benrahma had a chance to put the win beyond doubt for Nice when he was denied by Mandanda the visitors held on for a fifth win from their last six away matches to climb to sixth in the table.