ORLANDO, Fla. — Who’s No. 1?

Take your pick.

Depends on the week.

Professional golf has never been deeper or healthier than it is at the moment, and all you need to do is take a peek at the powerhouse Arnold Palmer Invitational leaderboard after Thursday’s opening round for proof.

Jon Rahm, who happens to be the No. 1-ranked player in the world at the minute, left the Bay Hill back nine scorched earth with an eagle-birdie-birdie on Nos. 16, 17 and 18 to cap a 31 on his back nine charge to finish 7-under-par 65 and with a one-shot lead.

Rahm leads Cameron Young, the pride of Sleepy Hollow in Westchester, Chris Kirk, last week’s Honda Classic winner, and Kurt Kitayama by two shots after all posted 5-under 67s.

Not far behind the burly 28-year-old Spaniard is Scottie Scheffler, the No. 2-ranked player in the world, who’s three shots back at 4-under.

Patrick Cantlay, ranked fourth, Xander Schauffele, ranked sixth, and Jordan Spieth, ranked 17th, are also all at 4-under and just three shots behind Rahm. Add in Rickie Fowler and Keegan Bradley at 4-under and what you have is a leaderboard stacked with stars.

As for the No. 1-world ranking, it’s become as elusive as it’s ever been, changing hands more often than $10 bills at weekend Nassau matches at the local clubs.

This is the first time since the inception of the Official World Rankings in 1986 that No. 1 has changed among three players (Rory McIlroy, Scheffler and Rahm) before March in a calendar year.

Scheffler returned to No. 1 in the world by winning in the Waste Management Open in Phoenix with Jon Rahm on the chase. A week later, Rahm took over No. 1 by winning the Genesis Invitational at Riviera in a tense battle with Max Homa, who is ranked eighth and is one of the hottest players in the world.

Among the top-ranked players, McIlroy was the only one not to hold up his end on Thursday, struggling to a 1-over 73 thanks, in part, to a messy double bogey on the risk-reward par-5 sixth hole, where his tee shot landed in the lake.

Scheffler can regain the No. 1 ranking this week with a win and Rahm not finishing any better than solo second and he can get it back with a runner-up finish and Rahm finishing worse than a two-way tie for ninth.

McIlroy can take over No. 1 with a win and Rahm finishing worse than a two-way tie for fifth.

“If I was purely a fan of the game and I see what’s going on, especially at the top, I think it’s a pretty cool thing,” McIlroy said before the tournament began. “I’m just happy to be in that conversation.”

Rahm’s win at Riviera was his fifth title worldwide in his last nine tournaments. Scheffler won four times in a two-month stretch last year — a run that included winning at Bay Hill and then winning the Masters.

How confident is Rahm?

When asked before the tournament if he felt anyone could beat him when he was “firing on all cylinders,’’ he replied: “No.”

Rahm, playing in the afternoon wave with Kirk, Young, Scheffler and Spieth having already posted their scores, birdied his first three holes and looked like he was going to boatrace everyone. His round, though, cooled until he went 5-under on his final seven holes.

Asked about his patience, Rahm said, “You just come out here and you know. You have to take it very much in stages.’’

“That’s what I think I did really well,’’ he went on. “Even when I was in the fairway, I picked my battles. You pick your battles and hope you can birdie the ones that you pick.’’

Rahm said before the tournament that he watched how Tiger Woods, an eight-time winner at Bay Hill, methodically dissected the course en route to winning.

Asked how comfortable he is on the course, Rahm said, “As comfortable as one can be at times. Some holes were very, very comfortable. Others are obviously very nerve-wracking at times. As comfortable as one can be.’’

Rahm comfortable on a golf course is not something his competitors want to hear.

Scheffler, asked about his motivation to return to No. 1, said, “I don’t like losing to people and any time you don’t win an event you’re always motivated. Any time you get some really good competition it’s very motivating. I got the one in Phoenix and then Jon went out the next week and beat me by a bunch of shots [at Riviera]. So, it’s fun to have guys playing at the top of their games.”

Rahm hasn’t finished out of the top 10 since August at the Tour Championship.

“If it’s not a win, they’re contending,” McIlroy said of Rahm and Scheffler. “Very rarely have you seen these guys in the past 12 or 18 months outside of the top 10, top 15, top 20. Just that relentless consistency week after week, month after month, building a really great body of work.”

Who’ll be No. 1 come Sunday night?

Stay tuned. The theater figures to be compelling.