Richy Werenski sank a short birdie putt on the par-5 18th for an 8-under 63 and a one-shot lead over Michael Thompson through one round of the PGA's 3M Open in Minnesota.
The 24-year-old Werenski is winless in on the PGA Tour and ranked 248th in the world. He broke a tie with Michael Thompson with his ninth and last birdie on the warm, windy afternoon at the TPC Twin Cities.
Dustin Johnson withdrew because of a back injury after a 78.
Johnson's departure comes after he posted back-to-back 80s last week at the Memorial for the highest 36-hole score of his pro career.
with files from Associated Press