While at the Gaillette, short for the Centre Technique et Sportif de la Gaillette, Lens's youth academy, Situ established himself as one of the club's top youth prospects, alongside fellow defender William Rémy and midfielders Alexandre Coeff and Mehdi Abeid.
While playing with the national under-16 team, Situ, alongside Rennes starlet Jérémy Hélan, drew the interest of Premier League clubs Manchester United, Chelsea, and Liverpool, as well as Portsmouth.
Manager Jean-Guy Wallemme, instead, allowed the young player to get some stable playing time in the Championnat de France amateur, the fourth division of French football, with the team's reserve squad.
Situ made his debut in the reserves opening match against Vesoul Haute-Saône, appearing as a substitute.
He started the match in the centre back position alongside veteran Ala Eddine Yahia and played the entire 90 minutes in the team's 1–0 victory.
Situ joined the under-18 team in August 2009, as an underage player, playing with his elder peers at the SBS Cup in the Japanese prefecture of Shizuoka.