In 2002, Sela reached the quarterfinals in the Australian Open Junior Competition and was in the top eight at the French Open Juniors. He won at Beaulieu Sur Mer. In 2003, his final year as a junior, he reached the quarterfinals at the Roland Garros Junior singles competition and won the French Open 2003 doubles title with partner Győrgy Balázs of Hungary. He made it to the semifinals at the US Open Junior Championships and won the Australia F1 tournament in Tasmania. In July he triumphed at the Togliatti competition in Russia, resulting in a new ATP ranking of 256.