There are a few ways that a win in a major can level up from being a notable victory to a building block for a legacy. First, there’s the locale; wins at Augusta or Pebble Beach or St. Andrews carry more gravitas than wins at … well, let’s not embarrass anyone. Then there’s the leaderboard; knocking aside the world’s best on Sunday holds more value than, say, beating four little-known guys who picked a good weekend to play the best golf of their life.

But there’s a third way: the moment. You know it when it arrives. The moment that the game’s biggest names rise to the challenge and claim it. Think Tiger Woods throughout the 2000-01 season … or, more recently, Bryson DeChambeau at the 2020 U.S. Open and Dustin Johnson at the 2020 Masters. Everyone’s watching, expecting the big dog to come through … and it happens.

We’re at one of those moments for two of the game’s best. Rory McIlroy and Jordan Spieth roll into the 2021 PGA Championship with a chance to vault their already-impressive careers into icon status.

For McIlroy, a fifth major would move him into a tie for 14th all-time, even with Phil Mickelson, Byron Nelson and Seve Ballesteros, and just two back of Arnold Palmer. For Spieth, a victory at the PGA Championship would give him the career Grand Slam at age 27, a feat only achieved by Tiger Woods, Jack Nicklaus, Ben Hogan, Gary Player and Gene Sarazen.

But for McIlroy, that’s the case at every major. For Spieth, every time the PGA Championship rolls around, the Career Grand Slam topic comes up. (Rory, missing the Masters, and Phil Mickelson, missing the U.S. Open, are the only other active players within one tournament of the mark.) So what’s different this time around?

Momentum. Both players are coming in strong … well, stronger than they’ve been in recent months, if not “strong” by their 2010s-era standards.

McIlroy won at the Wells Fargo earlier this month, his first victory in 19 months. But to him, it was almost a happy accident, a byproduct of taking a longer view of his career than week-to-week.

“Quail was awesome, it was great to get a win, but I’m thinking way beyond that,” he said Tuesday. “It’s funny, when you sort of think that way, something like that just sort of happens to fall into your lap. It’s almost like the less you try, the more things sort of go your way.”

And now he’s arrived at Kiawah Island, the site of one of his most famous victories, his eight-stroke win in the 2012 PGA Championship. How much of that weekend carries over to this one is debatable — McIlroy himself said he’s a completely different person now than he was when he hoisted the Wanamaker Trophy nine years ago — but McIlroy is the only player in the field who’s actually won a tournament at Kiawah. Comfort can go a long way with a player like McIlroy, and it doesn’t get more comfortable going into a major than a course you’ve already beaten … for what that’s worth.

“It seems like there’s been a lot of time that’s passed, and I feel like I’m a different person and a different player,” McIlroy said. “I played great here last time, obviously, and won my first PGA and my second major, but just because I did that doesn’t mean that I’m going to find it any easier this week than anyone else.”

Spieth wasn’t even a pro at the time of that last Kiawah visit. But he comes into the tournament with much more juice than McIlroy. Spieth spent nearly four years in the golf wilderness, dating back to the 2017 Open Championship, a winless time when “What’s wrong with Jordan Spieth?” articles were more prevalent than Spieth top-10s. But he’s undoubtedly found his groove again, posting seven top-10 finishes in his last nine tournaments, including a win at the Valero Texas Open.

“I’m not sure if there was a single turning point,” Spieth said Tuesday, speaking of his resurgence. “I think it was kind of a progression of finding some feels that allowed me to stand comfortably over the ball and hit a shot under pressure, and then doing that for multiple days in a row and then having that happen a couple tournaments in a row.”

This week, Kiawah sets up perfectly for his strengths. He doesn’t need to blast the ball to DeChambeau-esque lengths; he can rely on shot-shaping and his trusty putter to remain in the hunt. And when the winds come up, and they will, Spieth is one of the best American players at handling the wicked links-style gusts that will define this weekend at Kiawah.

One thing Spieth says isn’t on his mind: that career Grand Slam. “It’s not. It’s not. I think as we get into the weekend, if I’m able to work my way into contention, I think it’s something that’ll obviously be asked and come up, and it’s something that I certainly want,” he said. “I feel like I’ll have a lot of chances at this tournament, and if I just focus on trying to take advantage of this golf course, play it the best I can and kind of stay in the same form tree to green I’ve been in, all I can ask for is a chance.”

Here’s another reason why a victory this weekend could be so significant: based on prior experience, one major tends to lead to several more.

McIlroy and Spieth, two of the leaders for top dog in the post-Tiger era, have all clustered their major victories. McIlroy won four in less than four years. Spieth won three in less than three. (Brooks Koepka, the third challenger for that crown, won four in less than three years.) That may not be enough to constitute a trend, but unlocking one major win does seem to open the door to the possibility of several more. At the very least, it halts the “when will you win the next one?” questions for a year or so.

Only one of the two can possibly rise to the moment this weekend. But if he does, it’ll be a defining triumph in a Hall of Fame career.

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Jay Busbee is a writer for Yahoo Sports. Follow him on Twitter/Instagram/Facebook at @jaybusbee or contact him at jay.busbee@yahoo.com.

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