SAN FRANCISCO, 2 May 2015 (AFP) - The 25-year-old world number one only scraped into the last 16 at the death by coming back from two down with two to play to defeat Billy Horschel at the second extra hole of the closing round-robin games on Friday.
But there was no such jitters against Matsuyama who, like McIlroy, had won three straight to get to the tournament's knockout stages.
Both players birdied the par-five first before McIlroy holed from 25 feet for another birdie on the second to take the lead. A two-putt birdie from long range on the fifth was enough to take McIlroy two up.
Bogeys from a rattled Matsuyama at the sixth and seventh sent McIlroy racing clear at 4-up and the Northern Irishman birdied the eighth to go 5-up before Matsuyama finally grabbed some respite from the assault with a birdie two at the ninth.
But if the Japanese player harboured any hopes of staging an unlikely comeback they were all but snuffed out at the next hole when a rampant McIlroy chipped in for a winning birdie to restore a five-hole lead with eight to play.
Another birdie from McIlroy at the 12th made it mission impossible for Matsuyama and a one-sided contest came to an abrupt end two holes later leaving the Irishman still eyeing a quick detour to Las Vegas to take in the boxing showdown between Floyd Mayweather and Manny Pacquiao if he could finish his quarter-final in time.
"I'll need to play even better this afternoon to have a chance. There's two tickets and there's a plane waiting but whether I get on it or not we'll have to wait and see. But obviously this (the tournament) takes priority above anything else," said McIlroy.
In earlier last 16 results there were 2&1 wins for Gary Woodland over Australian Marc Leishman, for Australian John Senden over Hunter Mahan and for Englishman Tommy Fleetwood over South African Branden Grace.
Danny Willett pulled off an upset 3&2 win over countryman and former world number one Lee Westwood, who had put out Masters champion Jordan Spieth the previous day.
US veteran Jim Furyk was too good for JB Holmes, winning 5&3, while Rickie Fowler bounced back from an early deficit against South African Louis Oosthuizen to level the scores, but a poor approach to the 18th forced him to concede the tie.
Back-to-form Paul Casey made it three Englishmen in the last eight with a 3&1 triumph over South African Charl Schwartzel.
Scores at San Francisco's Harding Park golf course on Saturday in the last 16 of the $9.25 million WGC-Championship Match Play (x denotes ranking):
Gary Woodland (USA x52) bt Marc Leishman (AUS x60) 2&1
John Senden (AUS x65) bt Hunter Mahan (USA x32) 2&1
Tommy Fleetwood (ENG x57) bt Branden Grace (RSA x39) 2&1
Danny Willett (ENG x49) bt Lee Westwood (ENG x27) 3&2
Jim Furyk (USA x5) bt JB Holmes (USA x12) 5&3
Rory McIlroy (NIR x1) bt Hideki Matsuyama (JPN x16) 6&5
Louis Oosthuizen (RSA x30) bt Rickie Fowler (USA x13) 1-up
Paul Casey (ENG x37) bt Charl Schwartzel (RSA x38) 3&1