In 2005 Baldwin spent entire season with Class A Lakewood BlueClaws, where he led the South Atlantic League in innings pitched.

On August 20, 2006 he was traded to the Seattle Mariners with teammate Andrew Barb for the left-hander Jamie Moyer.

He spent the entire season with the Double-A West Tenn Diamond Jaxx where he led the Southern League with 166.0 innings pitched.

Dubbed "King of the Hill" by his teammates, Baldwin spent the entire 2008 season with the Triple-A Tacoma Rainiers.

In 2009 Baldwin spent the entire season with the Triple-A Tacoma Rainiers of the Pacific Coast League.