Braves reliever Luis Avilan left Tuesday night's game after delivering a pitch in the ninth inning of Atlanta's 6-3 win over the Royals.
The left-hander grabbed his left leg and fell to the ground while throwing a pitch, with the Braves later saying Avilan sustained a hamstring strain and cramping. He'll be reevaluated on Wednesday.
"Obviously, the way he fell down there, it doesn't look good," said Braves manager Fredi Gonzalez after the game.
The 23-year-old had allowed no runs in four innings of work over four appearances before Tuesday.
The Braves will now rely on left-handed reliever Eric O'Flaherty, who is the only other active left-handed reliever in the team's bullpen. Left-hander Jonny Venters is on the disabled list with an elbow injury and isn't scheduled to throw again for at least another two weeks.
Quinn Roberts is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.