The revered track outside Pittsburgh became waterlogged as storms caused three separate weather delays before play was called off for the day.
Only nine players finished their first round and more than half the field were yet to start, leaving American qualifier Andrew Landry, the world No. 624, top of the leaderboard.
The 28-year-old was three under par playing the final hole, one shot clear of world No. 4 Bubba Watson and Danny Lee, when the hooter went for the final time at 1551 ET on Friday.
American amateur Scottie Scheffler shot 69 to finish one under alongside Kevin Streelman, Lee Westwood and Harris English.
Defending champion Jordan Spieth was one over after 11, with third-ranked…