Juan Sebastián "Sebas" Saiz Soto (born 15 July 1994) is a Spanish professional basketball player for Alvark Tokyo of the Japanese B.League.

[1] Saiz, whose father is Spanish and his mother is from Dominican Republic,[2] started playing basketball at the youth teams of Real Madrid, until transferring to CB Talavera for personal reasons.

In 2009, he passed the trials to join Estudiantes, where he made his debut in senior competitions, playing in some Liga EBA games in 2011, at age 16.

Saiz moved in 2012 to the United States to continue his basketball career,[3] and in 2013 he joined the Ole Miss Rebels, averaging 5.1 points and 5.6 rebounds per game in his first season.

He ended his college years becoming only the second player in school history after Murphy Holloway to surpass 1,000 points and 900 rebounds and was included in the All-Conference first team of the Southeastern Conference.