For now, Stephenson is going to rest his arm.
"We're just waiting and seeing what develops the next couple of days," Reds player development director Jeff Graupe said from Cincinnati. "We'll keep monitoring him."
Cincinnati's first-round pick in the 2011 Draft, Stephenson was promoted to Louisville in July and has gone 4-2 with a 3.43 ERA in eight starts. For Double-A Pensacola, the 22-year-old was 4-6 with a 3.68 ERA in 14 starts.
Mark Sheldon is a reporter for MLB.com. Read his blog, Mark My Word, follow him on Twitter @m_sheldon and Facebook and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.