The right-hander made his Major League debut with the Cardinals during the 2008 season, going 0-1 with a 7.94 ERA (5 ER/5.2 IP) in four relief appearances. Worrell spent the majority of the season at Triple-A Memphis, where he went 3-3 with five saves, a 2.15 ERA (14 ER/58.2 IP) and 80 strikeouts in 53 games. He averaged 1.36 strikeouts per inning of work while limiting opponents to a .210 batting average.
Originally signed by St. Louis as a 12th-round selection in the 2004 First-Year Player Draft out of Florida International University, Worrell went 12-17 with 83 saves and a 2.95 ERA (92 ER/280.1 IP) in 242 relief appearances over parts of five minor league seasons in the Cardinals organization (2004-08). He has recorded 329 strikeouts in his 280.1 innings of work, averaging 1.17 strikeouts per inning pitched. In 2005, Worrell was named the Cardinal's Minor League Pitcher of the Year and was the winner of Minor League Baseball's Rolaids Relief Man Award. He was also selected to the Texas League and Pacific Coast League All-Star teams in 2006 and 2007, respectively.