Heston will have his contract purchased from Triple-A Fresno on Sunday. Heston already has a career-high 173 inning under his belt this season at Triple-A Fresno, over which he's posted a 3.38 ERA, 1.17 WHIP and 125:51 K:BB ratio. He'll serve as bullpen depth for the Giants down the stretch, and could be considered in an emergency spot start scenario.