When Matsuyama walked on the 18th fairway in the sunshine of a hot summer Georgia, he led by two strokes, had six kinds of lead as far as the twelfth hole, and needed to play safe to keep away from Will Zalatoris who played clear and waited in the clubhouse.
He completed the task after finishing two putts from one meter and won by one stroke after a 73-lap.
He showed no great feelings when he walked to friends who were all the happier.
Before the 15th par 5 hole, Matsuyama led with four strokes to teammate Xander Schauffele but hit flat and low over the green and the ball ended up in an underlying pond.
He got to drip and did bogey.
Schauffele hit a bunker for an eagle who just slipped past the cup and was able to make a simple birdie.
Before the last three holes, there were only two kinds of difference between Matsuyama and Schauffele.
Schauffele hit the water when he was going to challenge
On the 16th par 3 hole, it was Schauffele's turn to hit the water on the tee and his turn to drip.
The American then missed and knocked out the ball among the crowd who had to move quickly.
It ended with a triple bogey, -7 in total, and he was four strokes behind Matsuyama who did bogey.
The biggest threat to a Japanese victory was then from Will Zalatoris who at the same time reached the clubhouse in 70 strokes and finished at -9 after a 70-round to the great cheers of the audience.
Henrik Stenson was in 13th place before the last round of the day and had a good chance to be among the top twelve and get a free place for next year's competition.
Instead, the Swede, 117th in the rankings, took the elevator down the leaderboard after going around 76 strokes and finished in 38th place with +3 in total (73-71-71-76).