Roberto Castro is the leader following the first day of a rain-affected BMW Championship in Carmel, Indiana.
Play was suspended just before 20:00 local time (00:00 GMT) after heavy lightning and rainfall saw a postponement of over three hours.
Castro was able to complete his round with a seven-under-par 65 for the outright lead.
The 31-year-old American shot eight birdies before a bogey on the 18th proved his only blemish.
He holds a one-stroke lead over Brian Harman, who sits second after going bogey-free, including an eagle on the 15th.
Jason Dufner, U.S. Open champion Dustin Johnson and Chris Kirk - who only completed nine holes - are two strokes off the lead in equal third.
Rory McIlroy, the winner of last week's Deutsche Bank Championship, is tied for 10th at three under through 10 holes, along with Sergio Garcia - who completed his round.
Jordan Spieth is a further shot behind, also through 10 holes, while world number one Jason Day shot one over and sits tied for 51st.
The first round will resume on Friday and leads into the second, but more heavy rain is forecast for later in the day.