Matt Kuchar claimed a share of a three-way first-round lead at the Mayakoba Golf Classic as his wife also starred, caddying for Zach Johnson.

A bogey-free seven-under 64 took Kuchar to the top of the leaderboard on Thursday, where he was joined by Kramer Hickok and Dominic Bozzelli, but he saw his spotlight partially stolen by his spouse.

Johnson's caddie Damon Green was taken ill with four holes remaining, suffering in the Mexican heat, and Kuchar came to the rescue by recommending the watching Sybi.

She has taken on the role with the seven-time PGA Tour event winner previously.

"I didn't talk too much to Damon, but you could tell it was heat fatigue, heat exhaustion," Kuchar later told reporters. "It was really getting the best of him.

"I knew Sybi was in the crowd, I knew she had caddied for me before and was friendly with Zach Johnson. I figured she would be good to handle it and Zach would go easy on her.

"She knows the deal of keeping up and staying out of the way - and I knew Zach would be happy to see a friendly face to take over the bag."

Sybi Kuchar proved to be a lucky omen for Johnson, too, as he hit an eagle at the seventh to rescue an even-par 71.

A crowded field piled up behind Kuchar, Hickok and Bozzelli, meanwhile, with a huge 15-way tie for fourth just one shot back at six under.

Rickie Fowler ended the day at five under, with Tony Finau at two under and Jordan Spieth struggling at even par alongside Johnson after a wildly inconsistent round.