* Raonic took medical timeout in third set for wrist issue * Harrison to play Cypriot Marcos Baghdatis in third round (Recasts with quotes and detail) By Steve Keating NEW YORK, Aug 31 (Reuters) – Milos Raonic became the first major casualty of the U.S. Open when American qualifier Ryan Harrison shocked the Canadian fifth seed 6-7(4) 7-5 7-5 6-1 on Wednesday to reach the third round of the year’s final grand slam. The 24-year-old American, who beat Raonic once in their previous two meetings, came prepared to give the sixth-ranked Canadian a battle and proved the more durable during in a three hour, 37 minute match played in sweltering conditions. “The first two sets today were well over two hours, it was extremely physical,” said Harrison.