Born in Guédiawaye, Sylva spent nearly a decade at the service of AS Monaco FC, but featured mainly for the reserve team during his spell, being successively backup to Fabien Barthez and Flavio Roma in the main squad. He made his debut in Ligue 1 on 12 September 1999 in a 1–2 away against Stade Rennais FC, contributing with six appearances as the club won the national championship; he also served loans at Gazélec Ajaccio, SAS Épinal and AC Ajaccio before leaving in 2004, the latter two sides competing in Ligue 2.

Sylva earned 83 caps for Senegal, during nine years. His debut came on 6 June 1999, in a 2–2 draw in Burkina Faso for the 2000 African Cup of Nations qualifiers.

Sylva subsequently signed for Lille OSC on a free transfer, never appearing in fewer than 30 league games in his four years and helping his team to the second position in 2004–05. He retired in June 2010 at the age of 35, after two seasons in Turkey with Trabzonspor; although his contract with the former was due to expire in June 2009, according to Article 17 of FIFA’s regulations for the status and transfer of players he was allowed to leave the club.