Penny, who has been out since May 21 because of a strained right lat muscle, underwent an MRI exam which showed improvement in the injury.
"He's continuing to progress, but having an end date for when he'll be back, I've been wrong so many times, I'm just going to stay out of the guessing game," Mozeliak said. "What the MRI showed was significant improvement, and based on that, we're just going to continue down that path."
Penny has remained on a throwing program, but has not thrown off a mound since he was sidelined.
"He threw one day in L.A., but it just didn't sound like we were getting to where he was really getting any closer, so we decided to go back and do a study on him and let it be less subjective," Mozeliak said.