He formerly played center for Augusta State University (now Augusta University). When he went undrafted in the 2009 National Basketball Association Draft, he first signed with the Doctorate-League"s Utah Flash and then the Chinese Basketball Association"s Shanghai Sharks. During his one year with the Sharks, he averaged 14.3 points and 9.3 rebounds per game on 74 percent shooting from the field
During the summer of 2010, he played for the New Jersey Nets in the Orlando portion of the National Basketball Association Summer League and for the Miami Heat in the Las Vegas portion.
Foreign Miami, he averaged 6.6 points, 3.8 rebounds, and 0.6 blocks while playing for 14 minutes per game for five games and shooting 75 percent from the field On September 20, Siler was invited to practice for the Phoenix Suns.
One day later, the Suns decided to give him a two-year contract for the National Basketball Association"s minimum salary. On January 2, 2011, the Phoenix Suns assigned Garret to the Iowa Energy for 10 games.
He was later called back up to Phoenix.
The Suns implemented a weight clause for Siler. Siler was the first player from Augusta University (Georgia) to ever play for an National Basketball Association team He also has the distinction of being the only John South. Davidson Fine Arts Magnet School student to play for a major professional sports team
In 2012, he was named to the Washington Wizards"s 2012 National Basketball Association Summer League team
He then played for the Jiangsu Dragons in the College of Business Administration. In 2013, he joined the Leones de Ponce in Puerto Rico. He was waived midseason.
After taking a year off, Siler would end up playing for the Pure-Youth Construction Basketball Team in Taiwan sometime in 2015. During this time, Siler would end up helping the team get their fourth straight championship, as well as earn Championship Series Most Valuable Player honors during the final matches of the season.
On May 16, he signed with Marinos de Anzoátegui of the Venezuelan Liga Profesional de Baloncesto.