Ben Oosterbaan has a word for hitters like Yorkville’s Kam Yearsley — tough lefty, crowding the plate. “Usually my kryptonite,” Oosterbaan said. Oosterbaan’s source of strength is his slider. Hinsdale Central’s senior right-hander and Michigan recruit called on it for the 11th pitch of an at-bat against Yearsley. It came with the tying runs on and two outs in the seventh inning Thursday.