SAN FRANCISCO—Rory McIlroy, the world’s No. 1 golfer, drew three tough American opponents during group selection for the WGC-Cadillac Match Play Championship that begins Wednesday at TPC Harding Park. In Monday morning’s tiered blind draw, McIlroy’s Group 1 was filled out by U.S. standouts Billy Horschel, Brandt Snedeker and Jason Dufner.