By Rick Reeno

Former welterweight champion Carlos Quintana (29-4, 23KOs) has decided to call it a day. The Puerto Rican boxer announced his retirement on Saturday night, after suffering a fourth round TKO defeat to Keith Thurman (19-0, 18KOs) in an HBO televised fight at the Citizens Business Bank Arena in Ontario, California.

The 36-year-old boxer was often brought in as the opponent, but every so often he pulled a rabbit out of his hat and scored an upset win - as he did in 2006 when he decisioned an undefeated Joel Julio and then in 2008 when he scored a major upset with a decision victory over an undefeated Paul Williams. He was thrown in with Deandre Latimore earlier this year on the Floyd Mayweather-Miguel Cotto pay-per-view undercard, and once again scored an upset with a fifth round TKO win.