He left last Friday's game against Toronto with what the team called a strained shoulder. An MRI revealed that nothing is "structurally" wrong.
"A transient subluxation event in the setting of a fatigued shoulder," said medical director Dr. Thomas Gill on the Red Sox Web site.
Rest was recommended to strengthen the shoulder.
"I was listening for 'tear' and I heard 'no tear.' Basically that's all I was worried about, no tear in my rotator and no tear in my labrum," said Papelbon, who has an ERA of 0.92 ERA, 35 saves in 59 appearances. "I'm pretty positive that I will (pitch again this season). But if I can't, I'm not going to push it by any means."
"The news was a huge relief and besides the point of being relieved, I was thrilled," said Boston Manager Terry Francona.