Snell retired the first six hitters he faced Saturday, and eight of the first nine, but was unable to hold on to two separate leads as he struggled with control of his fastball and got behind on hitters.
With Saturday's loss, the southpaw fell to 0-4 on the season and his ERA rose to 4.71. He has pitched six innings in just one of his eight starts.
"I believe in myself a lot," Snell said following Saturday's start. "I'm aware of what I'm doing, and I need to be better. I know I can. So, it's frustrating that I'm not doing what I know I can do."
The right-handed Stanek, the organization's No. 16 prospect according to MLBPipeline.com, has made 14 appearances out of the bullpen for Durham this season, going 1-0 with two saves, a 2.00 ERA and 25 strikeouts in 18 innings.
Craig Forde is a contributor to MLB.com based in Boston. This story was not subject to the approval of Major League Baseball or its clubs.