If that's the case, he most likely will be the fifth starter and pitch his first game on April 11 against the Mets in New York.
Stammen has been a dominating pitcher this spring. In his last two games, for example, he hasn't allowed an earned run and has struck out eight batters in eight innings, showing that his elbow is 100 percent.
"I don't want to jinx anybody, but he has been really good," Riggleman said about Stammen.
Stammen scored valuable points with the organization by pitching most of last season with bone chips in his right elbow. He never asked out of the rotation, but the team forced him to stop throwing in late August so he could have elbow surgery.
Now, thanks to the surgery, Stammen can throw his breaking pitches without pain.
"Stammen probably has been the sharpest of anybody other than John Lannan -- without stating the obvious." Riggleman said. "I'm really happy for Stammen, because he is pitching without those bone chips. He pitched effectively for us last year, but now he is pitching more than that. He has been tough for hitters down here."
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.