Quantrill was promoted to Triple-A El Paso on Sunday, Jeff Sanders of The San Diego Union-Tribune reports.
Quantrill posted a 5.15 ERA with 101 strikeouts over 117 innings with Double-A San Antonio, so his promotion wasn't performance related. The Padres lost a couple of starters via the waiver wire Sunday, so the youngster was forced up a level to fill vacated rotation spots. He will get acclimated with the Pacific Coast League over the final month of the minor-league season, and could open the 2019 season back at that level.