Duncan earned his third U.S. Open start by virtue of being among the top five points leaders in the FedExCup standings not previously exempt for the championship. He tied for 56th in his previous U.S. Open appearance two years ago at Shinnecock Hills. Duncan registered his lone PGA Tour victory to day in the 2019 RSM Classic in a playoff over 2012 U.S. Open champion Webb Simpson. It was Duncan's first victory in a multi-day competition since the 2011 Indiana Amateur. Duncan is a 2012 graduate of Purdue University. His uncle and current swing coach, Andrew Johnson, won the 2005 Cleveland Open on the Nationwide Tour (now Korn Ferry Tour).