"That's Matty," manager Fredi Gonzalez said. "We all know what he can do."
After terrorizing left-handed pitchers over the course of five seasons for the Braves, Diaz signed a multiyear contract with the Pirates in December and struggled during the early months. But he has batted .421 against left-handed pitchers dating back to June 15.
Diaz made a second straight start for the Braves on Monday night, when they opposed Phillies left-hander Cliff Lee.