Santiago Casilla is a former professional baseball player who played as a relief pitcher in Major League Baseball (MLB). He was born on July 25, 1980, in San Cristobal, Dominican Republic. Casilla began his professional baseball career in 2000 when he signed with the Oakland Athletics as an amateur free agent.

Casilla spent several years in the minor leagues before making his MLB debut with the Athletics in 2004. He played for the Athletics for four seasons before being traded to the San Francisco Giants in 2010. Casilla played for the Giants for seven seasons, during which he helped the team win three World Series championships in 2010, 2012, and 2014.

Casilla was known for his versatility as a relief pitcher, as he was able to pitch in a variety of situations, including as a closer. He had a career record of 42-31 with an ERA of 3.29 and 144 saves. Casilla was also known for his ability to strike out batters, as he recorded 572 strikeouts in his career.

In addition to his success on the field, Casilla was also known for his leadership and positive attitude in the clubhouse. He was a respected veteran player who was often called upon to mentor younger players.

Casilla retired from professional baseball in 2018 after playing for the Giants, the Athletics, and the Texas Rangers. He finished his career with a record of 42-31, an ERA of 3.29, and 144 saves. Casilla was a valuable player throughout his career, and his contributions to the Giants' World Series championships will always be remembered by fans.