Bielak was promoted to Triple-A Round Rock on Friday, Chandler Rome of the Houston Chronicle reports.
The 23-year-old recorded a 3.75 ERA in 36 innings for Double-A Corpus Christi to start the season after posting a 2.35 ERA in 61.1 frames at the same level last season. Bielak profiles as a future backend starter with an average fastball, above-average command and two quality breaking balls (a slider and a curve).