The PGA Tour’s landmark agreement with LIV Golf cast a shadow over the U.S. Open at the Los Angeles Country Club and Phil Mickelson, who joined the Saudi-backed series last year, was an apparent target of some heckling on Thursday.

The fan was on the railing of the grandstand at the 18th hole and was heckling "Lefty" for more than 30 seconds, according to Sports Illustrated. The topics of the badgering were Mickelson’s deal with LIV Golf and an alleged sponsorship with Victoria’s Secret.

CLICK HERE FOR MORE SPORTS COVERAGE ON FOXNEWS.COM

Phil Mickelson chips

Phil Mickelson chips to the green on the sixth hole during the first round of the U.S. Open at Los Angeles Country Club on Thursday, June 15, 2023. (AP Photo/Lindsey Wasson)

Golf Magazine’s Dylan Dethier took a photo of the alleged heckler, who was wearing a sombrero.

The incident caused Mickelson to briefly lose focus but he finished up his round with a 69 and tied for 25th. Xander Schauffele and Rickie Fowler finished with a first-round 62 and set a record for the lowest score for a U.S. Open round in the tournament’s history.

JUSTICE DEPARTMENT NOTIFIES PGA TOUR OF PROBE INTO LIV GOLF MERGER: REPORT

Phil Mickelson swings

Phil Mickelson watches his tee shot on the 18th hole during U.S. Open at Los Angeles Country Club on Thursday, June 15, 2023. (AP Photo/Matt York)

"I played OK. I hit a few swings coming down the stretch, I made two bad swings that cost me a few strokes," Mickelson said, via Yahoo Sports. "But I hit a lot of good shots today. It’s a decent start, and I have a chance tomorrow morning to come out and shoot a good, solid round to get myself in position for the weekend."

As far as the LIV Golf deal goes, Mickelson said he didn’t want to talk about it just yet.

CLICK HERE TO GET THE FOX NEWS APP

Phil Mickelson gives thumbs up

Phil Mickelson gestures during the first round of the U.S. Open on Thursday, June 15, 2023. (AP Photo/Matt York)

"I don’t want to detract right now from this tournament and where I’m at," he added. "I’m playing well, I want to get myself in contention."