Puk was promoted to Double-A Midland on Thursday, Jane Lee of MLB.com reports.
Last year's first-round selection out of Florida showed he had little left to prove at High-A Stockton after fanning 98 batters in just 61.0 innings and allowing just one home run there this season. Puk will move up to Double-A Midland in the Texas League, where he'll have to adjust to a significant bump in competition level in an environment that tends to favor hitters. Still, Puk's promotion shows that he's a relatively quick riser in the A's system, even if he doesn't make it to Triple-A Nashville by the end of the season.