The Phillies said in a statement they were "disappointed" to learn about Stumpf's violation. "The Phillies support Major League Baseball's Joint Prevention and Treatment Program and are disappointed to hear today's news of Daniel's violation," the club said.
Stumpf's agent, Adam Groff, referred to the Phillies' statement, declining further comment.
Teammates expressed surprise.
"He's a good kid," left-hander James Russell said. "He doesn't seem like a guy that would knowingly put his career in jeopardy. You feel bad for him. You go from the ultimate high to the lowest low in a couple weeks. You feel really bad for him. I wish nothing but the best for him. We'll see how it plays out. I know everybody in the locker room is here for him if he needs us."
Stumpf's suspension does not affect his Rule 5 status with the Phils. He is eligible to rejoin the team July 10 in Colorado if there are no postponements.
Stumpf is the fifth Phillies player to be suspended for violating MLB's Joint Drug Prevention and Treatment Program. Antonio Bastardo, Freddy Galvis, J.C. Romero and Carlos Ruiz were the others.
The Phillies selected Stumpf from the Royals with the 12th overall pick in last year's Rule 5 Draft. He made three appearances in the Phils' first eight games. Stumpf allowed one hit, three runs, two walks and one home run in just two-thirds of an inning for a 40.50 ERA.
Stumpf allowed a grand slam to Reds third baseman Eugenio Suarez in his big league debut April 7. He threw one-third of a scoreless inning in each of his final two appearances.
Dehydrochlormethyltestosterone is an anabolic steroid also known as oral turinabol, which East Germany developed in 1962. It gained attention in the athletic world in the 1990s, when it was linked to German athletes.
Philadelphia recalled left-hander Elvis Araujo from Triple-A Lehigh Valley to take Stumpf's place on the 25-man roster.
Todd Zolecki is a reporter for MLB.com. Read his Phillies blog The Zo Zone, follow him on Twitter and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.