Troussier had been away from African football for six years following his decision to quit the Morocco national team in 2008 but the recently appointment Frenchman returned to oversee Sfaxien's Group B triumph.
Mohamed Ali Manser was the hero for Sfaxien in the all-Tunisian affair at the Stade Taieb Mhiri, scoring in the 77th minute for his fifth goal in four games.
The three-time CAF Confederation Cup champions, who parted ways with former coach Hamadi Daw recently, are now second in Group B with seven points from four games.
Sfaxien are one point adrift of Algerian leaders ES Setif, who they face in the final round, with two fixtures remaining.
ES Tunis are adrift at the foot of the table, having only collected three points after four matchdays.