The world No 3 was simply unstoppable from the moment he carded the only eagle of the day on the par-5 second hole at Firestone Country Club in Akron.
A second World Golf Championship title fast became a mere inevitability as he broke a plethora of records along the way with a superlative nine-under final round 61 and a 16 under total.
Over the course of the week, Matsuyama carded the most birdies ever in this event, his weekend aggregate total of 12 under is also the lowest ever score over the last two rounds in the famous tournament, while his remarkable 61 is the lowest final round in the history of the World Golf Championships - by three shots.
“Last night after the round, I went to the range and hit it really well and had a lot of confidence,” said Matsuyama. “Then I came to the golf course this morning and I don’t know where it went. It was probably the worst warm up I’ve ever had on a tournament that I’ve won.
“I was shocked, and the first tee shot showed it. I hit it left, but something about that shot, something clicked and from that point on, I was able to find it again.”
Two-time major champion Zach Johnson finished in outright second position after a two under 68 left him on 11 under, while American compatriot Charley Hoffman was a shot further back.
The leading European challengers – the joint third-round leader Pieters, world No 4 McIlroy and former WGC-HSBC Champions winner Knox – all began the day positively, but it all eventually unravelled and they were left in the shade.
Belgian Pieters (71) picked up a second top five in the WGCs this year - to add to another at the Masters - with a fourth-place finish on eight under, while Northern Irishman McIlroy (69) and Knox (68) of Scotland were a shot further back in a share of fifth alongside Adam Hadwin and Paul Casey.
McIlroy’s performance has given him encouragement heading into this week’s US PGA Championship - the season’s final major - at Quail Hollow in Charlotte.