Shuster was recalled from Triple-A Gwinnett on Tuesday.
Shuster will provide some immediate protection for the bullpen, but according to Mark Bowman of MLB.com, he's also a candidate to draw a start Sunday in San Francisco, depending on how/if he's needed leading into the weekend. The rookie left-hander holds a 5.00 ERA and 25:22 K:BB over nine starts with Atlanta this season.