Heston will start Wednesday against the Diamondbacks in place of Matt Cain (forearm), Henry Schulman of the San Francisco Chronicle reports. Cain has been diagnosed with a strained flexor tendon in his right arm and Heston will get the first shot at holding down his rotation spot, manager Bruce Bochy confirmed. Heston spent 2014 with Triple-A Fresno, going 12-9 with a 3.38 ERA, 1.17 WHIP and 6.5 K/9 over 173 innings. He had a 2.40 ERA and .192 BAA in 15 frames with the big club this spring.