STB Le Havre (2005–2010) Sy joined the French team
STB Le Havre in 2005. In 2009–10, his last season with Le Havre, Sy averaged 5.2 points, 1.7 rebounds and 1.3 assists in just over 14 minutes per game. On September 15, 2010, Sy signed a three-year contract with the Hawks, with the first year guaranteed at $473,604. Sy began his rookie season beset with injury, suffering an
Achilles injury during summer league. He subsequently missed all of training camp due to a bad back and was listed on the injury report for the first 18 games of the regular season before being cleared to practice. On December 27, 2010, the Hawks sent Sy to the
Utah Flash of the
NBA Development League. Sy made his debut for the Flash on January 2, 2011, in a 99–83 loss the
Bakersfield Jam. Sy notched six points, three assists and three rebounds in 25 minutes off the bench. On January 30, 2011, in a game against the
Austin Toros, Sy had his best game to date with the Flash, notching 22 points, 2 rebounds, and 1 assist in 26 minutes. On March 2, 2011, it was announced that Sy would return to the Hawks for the remainder of the
2010–11 season. Sy made his NBA debut against the
Indiana Pacers on April 8, 2011. He recorded a steal and a foul in 3 minutes. On December 23, 2011, Sy was cut from the
Atlanta Hawks.
France (2011–present) In August 2011, during the
2011 NBA lockout, Sy signed with
BCM Gravelines in France. His deal had an out-clause that would allow him to return to the NBA when the lockout ended. However, after he was cut by the Hawks during the pre-season, Sy re-signed with Gravelines on January 3, 2012. On June 27, 2012, Sy signed a two-year deal with
Le Mans Sarthe Basket of France. On May 21, 2014, he returned to BCM Gravelines signing a three-year contract. After two seasons he left Gravelines. On July 10, 2016, Sy signed a two-year contract with
SIG Strasbourg. ==National team career==