The Rays prospect recorded a season-high nine strikeouts and gave up three hits over six innings Friday as the Class A Advanced Charlotte Stone Crabs blanked the Tampa Yankees, 2-0.
It was Riefenhauser's first start since taking the mound against Bradenton on April 25. In two Florida State League starts, he's thrown 11 shutout innings, yielding five hits and two walks while fanning 17.
The 2010 20th-round Draft pick said he was fired up to get the opportunity to start, something he'd done almost exclusively last year between Class A Bowling Green and Charlotte.
"They told me about three or four days ago [that I'd be starting]," he said. "And I got a bullpen [session] in like three days ago. I was excited -- excited and nervous at the same time."
Riefenhauser said much of his success derived from the relationship he has with his catcher, Keith Castillo. The two spent the bulk of last season together at Bowling Green, where Riefenhauser made 18 starts before a promotion to the Stone Crabs.
"Me and [Castillo] are real comfortable together. I put the game mostly in his hands," said Riefenhauser. "I threw a lot of 0-1, 0-2 sliders that were working for me. Really, we just wanted to mix it up. He called a great game."
The 22-year-old left-hander has pitched 38 1/3 innings in 11 appearances this season, most of them in a long relief role. He's racked up 50 strikeouts while walking only five batters and sporting a league-leading 0.70 ERA.
Starting, coming out of the bullpen, long relief, short relief, Riefenhauser (6-0) has been asked to fill just about every role for Charlotte. And he hasn't had trouble adapting to any of them.
"It doesn't matter to me. I mean, I love to start, but it really doesn't matter," the New York native said. "I'm just happy when I'm out there pitching."
As a starter, Riefenhauser said his primary concern was being able to log enough innings to put the Stone Crabs in position to win and save the bullpen.
"I felt great about it, wanted to go at least five innings," he added. "That was my goal coming into the game -- keep the pitch count low, let my defense do the work, go five."
Rehabbing Major Leaguer Brandon Allen homered in the third for Charlotte. In addition to calling a good game behind the plate, Castillo went 3-for-4.