In Puerto Rico, Santiago plays professionally on the BSN with the Vaqueros. He has played in Bayamon since the middle 1990s, helping the team to various national championships and tournament finals. In between 1998 and 1999, he played for the Varese Roosters of the Italian league, and between 2000 and 2001, Santiago played for the NBA's Phoenix Suns in the position of back-up center, becoming the fourth Puerto Rican, after Butch Lee, Piculin Ortiz and Ramon Rivas to make it to the NBA. He was released from the Suns after the 2001 campaign was over. In 2003, he returned to the NBA, with the Milwaukee Bucks.
In 2002, Santiago represented Puerto Rico as a member of that country's national basketball team at the Indianapolis World basketball championships.