Atlanta selected Schwellenbach's contract from Double-A Mississippi on Wednesday.
Schwellenbach is set to make his major-league debut Wednesday versus the Nationals. The young right-hander has made eight starts between Single-A Rome and Mississippi this season, posting a 1.80 ERA, 0.91 WHIP and 51:10 K:BB over 45 innings. Just two of those starts came at the Double-A level and Schwellenbach will be skipping over Triple-A Gwinnett, but Atlanta felt the 23-year-old was ready to join its rotation. He should be in line for additional starts if he performs well.