There wasn't enough daylight for the pair to head back out and contest the three-hole aggregate play-off, meaning the pair will return at 9am local time Monday (midnight AEST) to decide the champion of golf's richest event.

McIlroy is chasing his second triumph at the PGA Tour's flagship event, while Spaun is chasing his second win on the American circuit.

McIlroy started the day four adrift but made his intentions clear from the get-go with a birdie at the par-4 1st hole and an eagle at the 2nd, leapfrogging Spaun, the overnight leader.

After the lengthy delay, McIlroy came out and carded a birdie on 12 but dropped a shot on 14 after a wayward drive. Spaun made a birdie on the same hole in the group trailing the Northern Irishman. The 34-year-old joining McIlroy in the lead with another birdie on 16.

Americans Lucas Glover and Akshay Bhatia hovered around the top of the leaderboard for a prolonged period. Towards the closing holes of the tournament, it was a two-horse race.

McIlroy and Spaun escaped the famous par-3 17th with pars and the equally as daunting par-4 18th with pars.

"I'm happy to be in the position that I am, but also, I feel like I had chances there on the back nine to close the door, and I didn't quite do that—a little bit of both. But I'm excited for the opportunity tomorrow," McIlroy said after his round.

JJ Spaun expects himself to win tomorrow. PHOTO: Getty Images.

"I guess it's very much just a three-hole match-play scenario. That's all it is. Just try to prepare as best I can tomorrow morning. Get a good night's sleep. It's been a very long day for all of us. Yeah, and just try to be as prepared as possible for tomorrow," he added.

Spaun was clearly relishing the big moment.

"I showed myself that I don't have to shy away from the moment," Spaun said.

"I think in the past I've done that, just kind of been afraid of being in that spotlight, being in that pressure, be worried about failure. But it's hard to win, and you have to fail multiple times in order to win.

"That's kind of what I've learned throughout my career, and it paid off today.

He knows the pressure is on McIlroy tomorrow, but that doesn't mean he has limited belief in getting the job done. He expects to be holding a trophy.

"I mean, everyone expects him to win. I don't think a lot of people expect me to win. I expect myself to win. That's all I care about."

Min Woo Lee was the only Australian to make the cut, finishing in a tie for 20th; New Zealand's Ryan Fox also finished in the collection of 10 players in the 20th spot at four-under for the tournament.

It will be the first Monday finish since Cam Smith’s win in 2022, before that; it had been 17 years since The Players entered a fifth day and the first play-off since 2015.

The three play-off holes are the par-5 16th, par-3 17th and the par-4 18th.