Phil Mickelson says he was not distracted by being heckled before teeing off in the LIV Golf Invitational Bedminster on Friday.
Mickelson stepped back from the tee after a spectator shouted "Do it for the Saudi Royal Family" at Trump National Golf Club Bedminster.
The six-time major champion was one of the highest profile players to sign a hugely lucrative deal with the Saudi-backed breakaway LIV Golf series, leading to him being suspended from the PGA Tour.
Mickelson was way down the leaderboard in a tie for 43rd after shooting a four-over 75 in the opening round of the third LIV Golf event in New Jersey, where debutant Henrik Stenson shares the lead with Patrick Reed on seven under.
The 52-year-old insisted he was not affected by the words of a vocal spectator before he took his first shot.
When asked if he was affected by being heckled, Mickelson said: "No. I had a really good day. The people here have always been great and treated me well.
"I had a really good day with the fans and with Henrik playing well, there was a lot of good things going on. I'm just a little frustrated with my game to be honest.
He added: "I'm just frustrated because I expect more of myself, so I'm gonna work until I get it fixed."
Asked again about the heckler, he replied: "I've always enjoyed playing in this area and we had a great day thereafter, I thought it was a good day all around, so I didn't really think much of it."
Stenson made a great start to his first LIV Golf event and was happy to be playing again after losing the European Ryder Cup captaincy due to his defection.
The Swede said: "It's nice to be out there playing golf, and yeah, of course it’s been a busy couple of weeks and not the most fun, but we keep our head down and focus on the golf."