Born in Sédhiou, Mané joined the French club Metz in the summer of 2011, initially as a reserve team player. He made his debut for the Championnat de France amateur side on 14 August 2011 in the 4–1 home win over Monts d'Or Azergues. Two months later, Mané scored his first goal for Metz B in the 4–0 victory away at Sarre-Union. After scoring twice in 12 league appearances during the first half of the 2011–12 season, he was called up to the senior team.
Mané played his first Ligue 2 match for Metz in the 0–1 home defeat to Bastia on 14 January 2012, coming on as a 75th-minute substitute for Kévin Diaz. He started the next game as the side drew 1–1 away at Châteauroux, before returning to the bench for the 0–2 loss against Sedan on 27 January. Mané went on to make 22 league appearances in total for Metz before joining Red Bull Salzburg at the start of the 2012–13 season.