Just brutal stuff here from Baseball America:
It was a debut to forget for Southisene. The Braves first-rounder hit .219/.242/.297 in 15 games with Low-A Augusta and had a brutal 27:1 strikeout-to-walk rate. Among 50+ PA hitters, Southisene ranked dead last with a .157 xwOBA. He was one of the most aggressive debut hitters with a 53.5% swing rate and a 37.5% chase rate. When he did hit the ball, it was often on the ground. The silver lining here is that Southisene’s contact quality was loud. His 105.4 mph 90th percentile exit velocity was second among all teenagers, narrowly behind Ethan Holliday (105.5).