In 2002, Harden began the year with the Single-A Visalia Oaks of the California League and was very impressive in 12 starts, as he had a 4–3 record with an ERA of 2.91, and struck out 85 batters in 68 innings. Halfway through the 2002 season, Harden was promoted to the Double-A Midland RockHounds of the Texas League, where he continued his impressive season, earning a record of 8–3, with an ERA of 2.95 in 16 starts. He also struck out 102 batters in 85 innings. His combined 2002 stats were 12–6, 2.93 ERA, 187 strikeouts and 75 walks in 153 innings.