Hagadone had the elbow examined after suffering the injury and is in the process of getting a second opinion.
"He threw a pitch and felt it. He was examined and it's not good," manager Terry Francona said. "We'll have more when we have more, but he looks like he hurt it pretty good."
Hagadone is no stranger to elbow injuries, he required reconstructive Tommy John surgery in 2008.
"Let's let him go get his second opinion, which is important," Francona said. "And then we'll have more. But, this isn't something that's probably a week with no throwing. I think he hurt himself."