When Hideki Matsuyama completed back-to-back Major Championship top-10 finishes as a 21-year-old in 2013 it was a hint that he possessed something special.
A year later he confirmed it, winning a first title on the PGA Tour, and he would complete a brace of victories in both 2016 and 2017.
Two of those triumphs came in World Golf Championship events and he didn't just win them, he dominated.
His 2016 success in the WGC-HSBC Champions saw him finish the week seven shots clear of the field.
The following summer he carded a sensational 61 to win the WGC-Bridgestone Invitational by five strokes.
A week later he landed a seventh Major Championship top 10; at the time, a win at the very highest level seemed inevitable.
Alas, the well has run dry: he's not only failed to add to that tally of Major Championship top 10s, he's also closing in on a four-year win drought.
Let's take a closer look at just how extensive the Matsuyama problem has become.
Form in 2021
The end of 2020 was not without hope for Matsuyama - he finished second at the Houston Open in his penultimate start and a week later was T13th in the Masters.
But 2021, although still brief, has largely been torrid.
Moreover, it's not just the bare results which hurt - it's the truth that he keeps recording his worst efforts on courses he has previously enjoyed.
He opened the year at Plantation for the Tournament of Champions, where previously he had, in three visits, only ever finished in the top four and had only once (in 12 laps) needed more than 70 swings.
He promptly opened with rounds of 73-75-72 and even a Sunday 68 couldn't rescue the situation: he ended the week T41st.
The Sony Open, a week later, offered hope: T19th was his second best effort at Waialae in eight starts.
But, when he hit the mainland, the struggles return.
He was T53rd at Torrey Pines in the Farmers Insurance Open, admittedly not his worst finish there (he's twice missed the cut), but it was his lowest finish in the six times he's made the cut.
On to TPC Scottsdale, for the Waste Management Phoenix Open, a course he won back-to-back on in 2016-2017, having finished top four there in both 2014 and 2015.
Admittedly, he only landed T15th and T16th in 2019-20, but his T42nd earlier this month was a much greater drop-off.
And now to Riviera.
He's played the Genesis Invitational six times and five times he finished T23rd or better, four times landing a top 12.
Even in 2017, when he missed the cut, he opened with a 68 to lie T19th: it was a second round 80 that did the damage, an off day so remarkable it suggests something was seriously amiss and it was an exception.
This Thursday he opened with a level-par 71 that left him outside the top 50 when he signed his card.
A fight to make the cut is on the cards, his old levels apparently beyond him.
Drop in wins, top fives and top 10s
Through 2015, 2016 and 2017 Matsuyama absolutely hit his straps.
He not only won six times in 73 starts worldwide, 38% of his starts reaped a top 10 and 30% of them a top five.
But in 2018, 2019 and 2020 he completed no win in 73 appearances, his top 10 rate dropped to 22% and his top five to 14%.
The contrast is marked: he's not only failed to add to his win column, he's not contending so frequently either.
Intriguingly, in 2014 (his first year on the PGA Tour) he had no wins, landed top 10s 22% of the time and top fives 15%.
So, which is his base level? Is the last three years a drop off from it - or a return to it?
In the Majors, the World Golf Championship and the world rankings
By the end of 2017 Matsuyama had chalked up seven top-10 finishes in 21 starts at the Major Championships.
Since then? Not one in 11.
What about the WGC?
Till the end of 2017 he had two wins in 16 appearances. Since then, just one top 10 in nine.
From late 2016 to mid-2018 Matsuyama began every week in the top 10 of the world rankings, claiming a high of second in mid-2017.
Since late-2018, he's spent most weeks outside the top 20 and is currently 22nd.
It's important to keep all of this in perspective.
Last year Matsuyama finished top 25 in all three Majors and also grabbed his first WGC top 10 since 2017.
Moreover, 16 PGA Tour top 30 finishes in 2020, including that second place at the Houston Open, would be considered a tremendous success by most golfers.
So, his results are still good. Very, very good in fact. They're just down on what he was producing.
In 2020 at least.
The results in 2021 are becoming a worry and therefore the rest of his week at Riviera will be instructive.
He needs to start turning the corner.