(REUTERS) - Jon Rahm retained his spot atop the Official World Golf Ranking this week, but the Spaniard's grip is precariously thin.

Collin Morikawa entered The Genesis Invitational with his third opportunity to claim the top spot for the first time in his career.

Morikawa, who also had mathematical chances to claim the No. 1 spot at the Hero World Challenge and the Tournament of Champions, needed to win last Sunday (Feb 20) and have Rahm finish worse than solo fourth.

Rahm, who made the cut on the number, rallied to tie for 21st at Riviera Country Club. That still left the door open for Morikawa, who made a spirited Sunday run before settling for joint-second.

Morikawa is now just 0.3398 points behind Rahm for the top spot. Patrick Cantlay, who entered the week with the same equation to wrest No. 1 away from Rahm, scuffled to joint-33rd after also making the cut on the number.

Cantlay remains No. 3, followed by Norwegian Viktor Hovland and Northern Ireland's Rory McIlroy. Scottie Scheffler and Justin Thomas each climbed a spot with top-10 finishes at the Genesis, with Xander Schauffele, Dustin Johnson and Japan's Hideki Matsuyama rounding out the top 10.

Chilean Joaquin Niemann vaulted 12 positions to a career-best 20th with his second PGA Tour victory. Australian Adam Scott also surged 12 spots to No. 34 with his T4, while PGA Tour rookie Cameron Young shot up 60 places to No. 53 with his joint-second.

Morikawa, who admitted in January that becoming No. 1 in the world rankings is a "dream" of his, entered Sunday eight shots off Niemann's lead. He shot a four-under 32 on the back nine to tie Rahm for the low round of the day with a 65 but ultimately was unable to catch the Chilean who led wire-to-wire.

"I just had to put together a few better rounds and make a few less mistakes," Morikawa said on Sunday.

"But overall, I'm happy with the way things kind of played out."