The Pirates announced that Burdi officially exited the game due to right elbow and bicep pain. Pirates director of sports medicine Todd Tomczyk said the team is "gathering information to get the most definitive diagnosis as to what's going on," according to Adam Berry of MLB.com.
Burdi collapsed to his knees on the mound immediately after delivering a ball to Jarrod Dyson in the top of the eighth inning, grabbing his right arm near his bicep. He appeared to be in tears while being examined on the field.
"It just takes the breath right out of you," Pirates manager Clint Hurdle told AT&T SportsNet after the game, according to WPXI's Alby Oxenreiter.
Burdi, a former Rule 5 Draft pick, was enjoying a stellar start to the season before suffering the injury. He entered Monday's game sporting a 4.32 ERA, minus-0.27 FIP, and 1.08 WHIP while averaging 18.4 strikeouts per nine innings over 10 relief appearances for the Pirates.
The 26-year-old has a history of arm issues and underwent Tommy John surgery two years ago while in the Minnesota Twins organization. He made his first two big-league appearances last September after rehabbing from the procedure.
Francisco Liriano replaced Burdi and completed the at-bat against Dyson.
The Diamondbacks won the game 12-4.