U.S. Open 2016: American Ryan Harrison pulls upset over ailing Milos Raonic

A U.S. Open field short on top-ranked homegrown men's players may have birthed a new American underdog story.

Ryan Harrison, not yet 25 and two years removed from his last top 100 ranking, has the makings of such a story after a spirited 6-7 (4-7), 7-5, 7-5, 6-1 upset of Milos Raonic, the No. 5 seed, in Wednesday's second round at Flushing Meadows.

Raonic was heavily favored but struggled physically in the New York heat, fighting through cramping in both his arms. At one point during the second set, he required medical treatment for the cramps, which had visibly affected him all match. Raonic blamed it on "nerves and stress" and said he was his own worst enemy, but Harrison also rose to the…