[6] Fosset began his football career at Cercle Athlétique Messin, which would merge with ASM to form FC Metz in 1932, which then obtained professional status and participated in the first French top division championship.

[1][3] Together with Albert Rohrbacher, Marcel Marchal, and Charles Zehren, Fosset played a crucial role in helping Metz become a stable team in the top division, and then reaching the national cup final in 1938, which ended in a 1–2 loss to league runners-up Olympique Marseille, but not without controversy.

[3][11] On 5 December 1937, in his second and last appearance for France, he played a crucial role in holding the reigning World Champions Italy to a 0–0 draw, as he muzzled their center forward Silvio Piola, a great specialist in the position.

[6] A similar incident had occurred a year earlier, in 1936, when during a trip to Marseille, the injured Fosset attended the match in the stands alongside its president, Raymond Herlory, and were "shocked" to hear OM supporters jeering at their team: "Bunch of Germans, go home".

[12] After the liberation of the city by the Allies, the club structures in Metz were rebuilt and Fosset served as its coach in the 1944–45 season, to only be paid after the first revenues had been collected; however, he was replaced shortly after by the Dutchman Beb Bakhuys.