Just five men achieved the career Grand Slam in 90 years, but two more could join the club in the space of a month if Jordan Spieth can follow Rory McIlroy's example.
McIlroy became the sixth member of golf's most exclusive club with his epic victory at Augusta National, and now Spieth will go in search of his one missing Major at the PGA Championship.
So there's nobody better for Spieth to draw inspiration, and advice, from than the only other man still playing regularly who knows what it takes to win all four Majors.
After a dominant 2015 when Speith won The Masters and US Open and had a chance to win all four, he added the Claret Jug at the 2017 Open to move just a Wanamaker Trophy away from the Grand Slam.
It looks like the US Open ship has sailed for Phil Mickelson, so after McIlroy won The Masters, Spieth is the only player just one Major away from a Grand Slam.
Winning a golf tournament is tough enough, winning a Major even harder, but winning the one remaining to complete a Grand Slam offers unique challenges, as McIlroy explained.
"You know that you're not just trying to win another tournament, you're trying to become part of history, and that has a certain weight to it," McIlroy said at the Truist Championship.
"I've certainly felt that at Augusta over the years. I'm sure Jordan has felt that a bit going into each PGA that he's had a chance to do the same thing."
A big difference between the two is that while McIlroy had to deal with demons and ghosts all around Augusta National, he was at least able to learn how to play the same course every year.
Spieth, by contrast, may not have the same pressure of trying to win the most iconic Major, and first of the season, but he does have to try and win on different courses every year.
"It's hard, I think, for Jordan having to do - you have to go back to the same tournament every year for Jordan, but not the same golf course," McIlroy added.
"I think it's a little bit of a different - it's a bit of a different proposition for him rather than me having to go back to the same venue every year and trying to, I guess, do that as well.
"As much as you try to get yourself in the right frame of mind to just try to win the golf tournament and then let everything else happen, it's in there. Consciously or subconsciously, you feel that.
"I said this to people, the worst I felt on Sunday at Augusta was probably when I held the birdie putt on 10 to go 4 ahead because I'm like, oh, I really can't mess this up now. There's that pressure."
Spieth's form has struggled in recent years, but a fourth-placed finish at the Byron Nelson after a Sunday 62 showed that he's in decent form ahead of his ninth Grand Slam bid.
