Gearrin is a side-arming 25-year-old who is receiving his first shot in the majors. He has toiled in the minors since 2007, including a full season of 80 innings with Gwinnett last year. To open a spot, the Braves demoted outfielder Matt Young to Gwinnett for the time being.
Gearrin's walk and strikeout numbers have taken hits in the upper levels, which may be expected with a side-armer who relies on ground balls. His K/BB dropped to 2.06 last season, recording a 3.36 ERA and 4.06 FIP. Like Moylan, Gearrin lives for grounders, but the Braves may not use him in the same situations as they would with Moylan due to inexperience. Gearrin is likely there just for reinforcement for a tired bullpen.
You can find my report on Gearrin here. (Hey, I got the ETA right!)
Young probably won't be at Gwinnett for long, just until the Braves get caught up innings-wise in the bullpen. That could possible come Friday when they return home following an off day.