Morikawa carded a closing 69 at The Concession Golf Club to finish 18-under par, three shots clear of Brooks Koepka, Viktor Hovland and Billy Horschel.

And there was a tribute to Woods, his golf idol growing up.

"We don't say 'Thank you' enough," Morikawa said, referring to how much Woods has raised the profile and prize money in golf.

He also mentioned his grandfather dying a month ago and began to get emotional.

Morikawa became the 24th player to win a major and a WGC title since this series began in 1999, joining Woods as the only players to win both before turning 25.

There were red numbers on the board and on the golf course, with several players including Australian Jason Day wearing red shirts and black pants – the Sunday colours of Woods – as a show of support as Woods recovers from career-threatening leg injuries from his car crash in Los Angeles.

"Obviously just paying respect to Tiger," Day said.

Cameron Smith rebounded from his horror third round to card a closing five-under 67 to be best of the Australians in a share of 11th, eight shots behind Morikawa.

It was another promising showing ahead of next month's Masters after the 2020 Augusta National runner-up was fourth at The Genesis Invitational.

Smith was the best of the Aussies, sharing 11th place. PHOTO: Mike Ehrmann/Getty Images.

Despite back-to-back top-20 finishes after missing the cut in his first two tournaments of the year, Day admitted he struggled to get his game going at the same time.

"The early part of this good was with the ball-striking, disappointed with the putting, and then the last two days were disappointed with the ball-striking and actually really good with putting," he said.

"So got to put those two together."

Morikawa didn't have the colours on Sunday but he had the game as he saw off the challenges of Koepka (70), Hovland (67) and Horschel (70), who even managed to fleetingly join the winner for the lead early in the final round.

Outside of a chunked chip on the 2nd hole that made him scramble for bogey, Morikawa didn't miss a fairway the rest of the way and was rarely out of position.

Scottie Scheffler shot a 68 to finish fifth while Rory McIlroy and Patrick Reed, both dressed in red and black, never got anything going.

McIlroy closed with a 71 to tie for sixth, while Reed shot a 72 and to finish another spot back.

Of the remaining Aussies in the field at the US$10.5 million (AU$13.5m) tournament, Min Woo Lee (72, tied-28th) was next best ahead of Marc Leishman (71, tied-39th), Jason Scrivener (75, tied-41st), Wade Ormsby (72, tied-52nd), Adam Scott (77, tied-54th), Brad Kennedy (73, tied-61st) and Lucas Herbert (74, 70th).