Unheralded J.J. Spaun outshined the game's top players and led the U.S. Open by one shot after the first round on Thursday at steamy Oakmont Country Club where the big names like Scottie Scheffler, Bryson DeChambeau and Rory McIlroy all struggled.

Much of the talk this week has been about how the notoriously challenging course would keep scores in check, and while the layout did bare its teeth, Spaun managed the day's only bogey-free round and the eighth ever in a U.S. Open at Oakmont.

Spaun, who lost to McIlroy in a playoff at The Players Championship in March, fired a 4-under-par 66 that marked his lowest round in a major and left him one shot clear of South African Thriston Lawrence.