Burnes (elbow) threw a bullpen session Tuesday, Jose M. Romero of the Arizona Republic reports.
Burnes has been throwing occasional bullpen sessions since spring training -- Tuesday's session was his fourth -- so there was nothing particularly notable about Tuesday's activity. "He just wants to make sure everything is feeling right, he's duplicating his delivery," Diamondbacks manager Torey Lovullo said of Burnes. The pitcher is still on track to return near or after the All-Star break.