[5][1] He made his MLB debut with the Phillies on August 7, 2001, in a home game versus the San Diego Padres, at Philadelphia's Veterans Stadium.

[1] On November 3, 2003, the Phillies traded Duckworth, along with minor leaguers Taylor Buchholz and Ezequiel Astacio, to the Houston Astros for Billy Wagner.

[1] On April 28, 2007, Duckworth picked up the only save of his MLB career, going three innings of shutout baseball to close out a 8–3 victory over the Seattle Mariners.

[12] However, in January 2008, he was designated for assignment by the Royals to make room on the organizational roster for free agent signee Brett Tomko.

[13] On August 24, 2008, Duckworth was recalled by Kansas City to start;[14] in his first game, he went five innings while giving up three earned runs, and was credited with the win.

In January 2010, Duckworth signed a minor league contract to return to the Philadelphia Phillies organization.