LOS ANGELES (AP) One of Jason Day's goals at the start of the year was to stay at No. 1 for the entire calendar year. The year is not even two months old, and already he is facing his first big challenge.
And not just from one player.
Dustin Johnson, coming off a third-place finish at Pebble Beach, and Phoenix Open champion Hideki Matsuyama both have a mathematical chance to reach No. 1 in the world by winning the Genesis Open at Riviera. Johnson would need Day to finish around fourth or worse, while Matsuyama could reach the top only by winning and Day finishing about 25th or worse.
Tiger Woods in 2009 was the last player to start and finish a year at No. 1.
Rory McIlroy was the last player to stay at No. 1 for longer than a year, starting with his victory at the 2014 Bridgestone Invitational and ending when Jordan Spieth passed him with a runner-up finish in the 2015 PGA Championship.
Just don't get the idea Day is consumed with the ranking.
''I said earlier that a calendar year would be great to go No. 1, but I need to just focus on what I need to do because you can't really focus on staying No. 1,'' Day said. ''The more you focus on the actual target itself, the more you attach yourself to it, you make mental errors out there, you get more frustrated, you do silly things on the golf course that you shouldn't be doing.''
Johnson also had a mathematical chance to get to No. 1 last week, but he would have had to win Pebble and have Day finish out of the top 50. Day tied for fifth. Johnson also had a chance at the PGA Championship last summer, but he missed the cut and Day was runner-up.
Day doesn't have a lot of history at Riviera. The only reason he is playing is because of the tour's new ''strength of field'' regulation that requires most players to compete at an event they haven't been to in four years.
His best finish is a tie for 62nd.
He keeps reminding himself that he didn't have a great history at Bay Hill and The Players Championship, and he won them both last year.
DAVE MUSGROVE: The European Tour lost another legendary caddie when Dave Musgrove died Monday at age 74.
Musgrove and Dave Renwick, who died last year, are the only caddies to work for three major champions. Musgrove was on the bag when Seve Ballesteros won his first British Open in 1979. He worked for Sandy Lyle when the Scot won the Open in 1985 and the Masters in 1988, and he was alongside Lee Janzen when he won his second U.S. Open title at Olympic Club in 1998.
Musgrove renewed his partnership with Janzen in 2001 so that he could caddie in his 40th consecutive British Open.
Among the many players paying tribute on Twitter was Lyle, who said, ''We wrote history together at The Open, The Masters and The Players Championship. We'll miss your humour and your stories.''
NICKLAUS TRIBUTE: The end of the Masters coincides with the start of Golf Channel's latest project, a three-part series on Jack Nicklaus.
The Golf Films project is called ''Jack,'' and it will air over three straight nights in prime time starting at 9 p.m. on April 9. It will feature nearly 100 interviews and hundreds of hours of archived film.
''`Jack' is a project that Golf Films has spent years developing in order to comprehensively capture the career and legacy of golf's most accomplished champion,'' said Mike McCarley, president of golf for the NBC Sports Group.
The first part will be the early part of his career, including the relationship with his father, meeting his wife and early success. The second part will look at the his playing career, highlighted by his 18 major championships. The final part looks at his legacy in the game, from the priority he placed on family to his golf course design and work with Nicklaus hospitals.
It is being produced by Israel DeHerrera, who also produced the three-part series on Arnold Palmer that was broadcast in 2014.
RACE FOR MEXICO: The first World Golf Championships event is around the corner in Mexico City, and this week will start determining who gets there.
The field will be determined by the top 50 in the world ranking after this week. Thomas Pieters (No. 47) and Shane Lowry (No. 51) are among those playing the Genesis Open at Riviera, which has the strongest field of the year so far.
The tighter race is the FedEx Cup standings. The top 10 after the Honda Classic will be exempt. Hudson Swafford at No. 8 and Gary Woodland at No. 11 are separated by only 61 points with two weeks to go. Rod Pampling, currently No. 10, has not played in a WGC event since 2009.
On the European Tour, Pablo Larrazabal is holding down the 10th spot. He has to stay there at the end of this week to make the Mexico field.
Much like Chinese players in the HSBC Champions in Shanghai, the WGC-Mexico Championship is reserving a spot for the highest-ranked Mexican player. That would appear to go to Roberto Diaz, who lost in a playoff on the Web.com Tour last week in Colombia. That enabled Diaz to move from No. 719 to No. 462. He currently is 36 spots ahead of the next Mexican player, Rodolfo Cazuabon Jr.
Among those playing the Web.com Tour event in Panama this week who could pass Diaz are Carlos Ortiz and Abraham Ancer.
BODY LANGUAGE: Hideki Matsuyama doesn't always look happy with his golf shots, even when they turn out well. Such was the case at the Phoenix Open, when the Japanese star would finish with one hand on the club only for the ball to finish in reasonable range for birdie, or his shoulders would slump and the ball would split the middle of the fairway.
''Sometimes how you're playing and the results don't coincide,'' Matsuyama said. ''So for me, when I do a one-handed finish, to me it's a missed shot. It's just the result was good.''
When he was jokingly asked if he did that to confuse the television announcers, Matsuyama smiled and said, ''No. That would be fun.''
DIVOTS: Jordan Spieth's nine PGA Tour victories have come at eight tournaments. The only place he repeated was the John Deere Classic. Tiger Woods did not win the same PGA Tour event until his 10th victory at the 1999 Western Open. ... The first team event on the PGA Tour since 1981 will have official prize money, but not world ranking points. The Official World Golf Ranking board denied a PGA Tour request to offer points at the Zurich Classic this year. ... Charles Howell III has had 46 finishes in the top 10 since his last PGA Tour victory at Riviera 10 years ago. ... Sahith Theegala of Pepperdine earned a spot in the Genesis Open with a 69 at Riviera on Monday to win the Genesis Open Collegiate Showcase.
STAT OF THE WEEK: Brandt Snedeker has earned $6,821,882 at Torrey Pines and Pebble Beach, or 21.7 percent of his career earnings.
FINAL WORD: ''He's a rock star. And I can say that, because I know quite a few rock stars.'' - Country singer Jake Owen on Jordan Spieth.