Powell spent all of 1996 with the Single-A Delmarva Shorebirds where he went 12–9 with a 3.02 ERA, enough to earn a promotion to High-A West Palm Beach to begin 1997.

In 1998 with the Double-A Harrisburg Senators, he went 9–7 with an ERA of 3.00 and was promoted to the major leagues for the first time after the All-Star Break.

Powell made his major league debut on July 23, 1998, but lost despite giving up only 1 run in 6 innings.

Powell was assigned to the minor leagues to begin 2001, but after going 4–2 with a 1.59 ERA and a .77 WHIP in 11 starts, he went to Japan to play.

He signed with the Osaka Kintetsu Buffaloes of Nippon Professional Baseball where after a shaky first season, he became one of NPB's most successful pitchers.

In January 2009, Powell left Hawks and signed a minor league contract with the Pittsburgh Pirates.