 His performance got him promoted that same year to AAA ball with the Tacoma Rainiers in the Pacific Coast League.Thornton had a shaky start to his career in Triple-A ball, starting 2 games and posting an 0–2 record and an 8.00 ERA.Thornton stayed with the Tacoma Rainiers in and posted a 7–5 record, along with a 5.20 ERA and 74 strikeouts in 83 innings pitched.