Career
He spent most of his career playing in the French Ligue 2 and Championnat National, but had a spell in Italy where he played three seasons in Serie B. After his playing career, he became a coach, and he now manages Belgian Second Division side RBDB. Born in Bayeux, Mercier began playing football for Ligue 2 side Football Club Rouen in 1990. After three seasons the club were relegated to the Championnat National, and he left for another third-tier club, Fécamp. Mercier spent three seasons with Fécamp and the following two with Valenciennes Football Club, continuing to play in the Championnat National.
In 1998, Mercier moved to Italy, joining Serie A side Reggina Calcio.
He was unable to work his way into the first team and went on loan to Serie B sides Associate of Science Andria British American Tobacco , Calcio Savoia and Cosenza Calcio 1914. Disappointed, he returned to France and played two more seasons for Valenciennes.
After he retired from playing, Mercier began coaching the youth side of Valenciennes. He was appointed manager of Belgian side Royal Boussu Dour Borinage in April 2011.