At the start of the 2007–08 season, Mensah started in the first three league matches before suffering a thigh injury that kept him out for a month. However, during a 1–0 win against Saint-Étienne on 15 August 2007, he suffered a thigh injury that kept him out for a month. It was not until on 16 September 2007 when Mensah returned to the starting line–up, starting the whole game, in a 1–0 win against FC Lorient. Since returning from injury, he regained his first team place for the rest of the 2007 despite being on two occasions. Mensah also made his European debut, starting the whole game, in a 1–1 draw against Brann on 9 November 2007. After spending a month, due to international commitment, it was not until on 16 February 2008 when he returned to the starting line–up, as Stade Rennais lose 3–1 against Lille. Mensah was later appointed as the club's captain for the rest of the 2007–08 season after being appointed by Guy Lacombe, as well as, regaining his first team place since returning from international duty. It was not until on 10 May 2008 when he scored his first goal of the season, in a 2–1 win against Toulouse. Despite missing two more matches later in the 2007–08 season,