An MRI on his throwing arm revealed no tears or breaks. Burdi did, however, suffer a strained biceps tendon and flexor mass during a scary moment on the mound Monday against the Arizona Diamondbacks, a source told ESPN's Jeff Passan.
The Pirates placed Burdi on the injured list Tuesday with right biceps/elbow pain, the team announced.
In the eighth inning, Burdi hurled a 97-mph fastball and immediately crouched over in pain before falling to the ground while grasping his right arm.
Trainers attended to him, and he was escorted off the field in tears.
The injury is expected to sideline Burdi indefinitely, but it won't require surgery.
Because he experienced so much pain, Burdi plans to seek a second opinion to ensure rehab on his surgically repaired arm is the right path forward, a source told Passan. He underwent Tommy John surgery two years ago while in the Minnesota Twins' organization.
The 26-year-old has posted mixed results this season, allowing nine earned runs in 8 2/3 innings while striking out 17 batters.