Jordan Spieth tees off in next week's Open at St Andrews taking the third and biggest step in his bid to achieve golfing immortality by winning all four majors in the same calendar year.
But, regardless of whether world number one Rory McIlroy will be fit enough to challenge him or not, one of his past opponents believes he can do it.
England's Andy Sullivan lost to Spieth as an amateur at the 2011 Walker Cup.
"What he's achieved since has not surprised me one bit," admits Sullivan.
The European Tour professional from Nuneaton, beaten 3 & 2 by an 18-year-old Spieth in the Sunday afternoon singles almost four years ago but still on the winning team at Royal Aberdeen, told BBC Midlands Today: "I gave him absolutely everything that day and he still came back with more.
"The Walker Cup that week was an unbelievable thing to be a part of. There were a lot of good guys in that US team. Harris English, Peter Uihlein and Russell Henley have all been winners on tour now.
"But you knew Jordan Spieth had got pedigree. You knew he was going to be a quality player."
Having both turned professional following that Walker Cup, Sullivan found himself in the same field as Spieth for the first time at a major championship when he qualified for last month's US Open at Chambers Bay, missing the cut by just one shot on the outskirts of Seattle, in Washington State.
Now he is set to make his Open Championship debut at St Andrews ranked 54th in the world (England's seventh highest-ranked golfer) thanks largely to the two European Tour victories he enjoyed in South Africa in the space of two months earlier this year.
The second of them, at the Johannesburg Open in March, was also part of the Open Qualifying Series, to earn Sullivan his ticket to St Andrews' famous Old Course.
"I've played St Andrews a lot as an amateur and also in the Dunhill Cup," he added. "So I'm going there with confidence. Having a chance of winning would be unbelievable, a dream. But my first objective is to make the cut and then to look at getting into the top 10."
As for world number two Spieth's chances of adding to the major victories he claimed at The Masters at Augusta in April and in last month's US Open, Sullivan says: "The Open is going to be a different challenge to Chambers Bay and the Masters.
"The weather is going to be a factor. It's more unpredictable in Scotland.
"If he wins that one too, you'd fancy him to go and do the Grand Slam but there'll be a lot of players looking to take it away from him."
Andy Sullivan spoke to BBC Midlands Today's Ian Winter, prior to world number one Rory McIlroy suffering the ankle injury that threatens to rule him out of the 144th Open Championship.