Seth Johnston hit .233 across 108 games with the San Antonio Missions. He went 87-for-373 with 12 doubles, two triples, nine homers, 37 runs scored and 54 RBI. He posted a .295 on-base percentage with a 32-to-89 walk-to-strikeout ratio. He stole five bases in nine attempts and committed 12 errors in the field. He hit .231 in 130 at-bats with runners in scoring position and grounded into 10 double plays. Johnston was tied for second on the team with six sacrifice flies.

Seth Johnston hit .375 across nine games with the Portland Beavers. He went 12-for-32 with three doubles, four homers, six runs scored and six RBI. He posted a .412 on-base percentage with a 2-to-8 walk-to-strikeout ratio. He hit .200 in five at-bats with runners in scoring position and grounded into one double play.

2008

Johsnton hit .250 with 115 hits in 460 at-bats with the San Antonio Missions. He collected 25 doubles, 16 homers, 67 runs scored, and 66 RBIs across 127 games. He also drew 40 walks compared to 91 strikeouts for a .309 on-base percentage and stole four bases in six attempts.

2007

Johnston hit .292 with 106 hits in 363 at bats for the Lake Elsinore Storm. In 95 games he had 19 doubles, four triples, eight homers, 56 runs scored and 51 RBIs. He drew 36 walks compared to 82 strikeouts.

Johnston hit .184 with four doubles, three runs scored and seven RBIs over 12 Storm playoff games.

2006

Seth Johnston went 1-for-10 with a run scored and four K's in a three-game rehab assignment with the AZL Padres.

Johnston hit .275 with 126 hits in 458 at bats for the Fort Wayne Wizards. In 112 games he collected 33 doubles, ten homers, 58 RBI's and 72 runs scored. He also drew 32 walks while whiffing 80 times.

2005

In 47 games for the Ems, Seth Johnston hit .253 with eight doubles, one triple and two homers. He knocked in 23, including seven in one game, and scored 15.

Johnston was taken in the fifth round of the 2005 Draft by the Padres. Johnston had a successful career at Texas, going to the College World Series all four years.