Australia's Jason Day hit a stunning wedge to 18 inches on the sixth extra hole to beat Alex Noren and claim the Farmers Insurance Open in a Monday finish at Torrey Pines.

The former US PGA champion and world No 1 got back into the winner's circle for the first time since he claimed the 2016 PLAYERS Championship 20 months ago and moved up four places to tenth in the world rankings.

Day (70), 54-hole leader Noren (73) and American Ryan Palmer (70) tied on 10-under par on the South Course at Torrey Pines on Sunday.

But while Palmer was eliminated after making par on the first extra hole, the 18th, Day and Noren could not be separated after another four holes.

Play was suspended until Monday morning, and it was Day who claimed his 11th PGA Tour win, sinking an 18-inch birdie putt on the sixth playoff hole at a near-deserted venue — his fourth birdie on the par-five hole in the playoff.

According to reports, spectators weren't allowed in because organisers said they didn't have time to arrange for security.

Noren tried an aggressive second shot from the first cut, but his ball landed short of the green and rolled into Devlin's Billabong.

Day, meanwhile, hit his second shot out of the rough and over some trees onto the fairway before spinning a wedge back to 18 inches from the cup.

Noren dropped in the fairway around 40 yards from the pin but failed to hole out for birdie and then missed for par before Day tapped in his short putt for victory.

“It’s been a long time coming,” Day said, who battled injury and the upset of his mother's cancer diagnosis last year. 

“I know last year wasn’t the best year for me. …I worked hard in the offseason to get back in this position.”

On Sunday, Day and Noren birdied the par-five 18th all three times they played it – on the first second and fifth playoff holes – and made par on the par-three 16th and par-four 17th holes.

The top seven in the world rankings remain unchanged, but Rory McIlroy rises three places to eighth following his runner-up finish in the Omega Dubai Desert Classic with champion Li Haotong becoming the first Chinese golfer to break into the world's top 50 following his 28-places jump to 32nd.

Noren moved up three places to 16th but Shane Lowry fell three places to 67th following his missed cut in San Diego while Paul Dunne dropped two spots to 76th after missing the five-under-par cut by one in Dubai.

Tiger Woods share of 23rd moved him up 108 places to 539th in the world while McIlroy's second-place finish also moved him up to eighth in the European Ryder Cup World Points List, bumping Dunne out of the top eight automatic places in Thomas Bjorn's team.

Lowry is the only Irishman in action in this week's Waste Management Phoenix Open while Darren Clarke flies the flag in Malaysia in the European Tour's Maybank Championship at Saujana Golf and Country Club.

Official World Golf Ranking

1. Dustin Johnson
2. Jon Rahm
3. Jordan Spieth
4. Justin Thomas
5. Hideki Matsuyama
6. Justin Rose
7. Rickie Fowler
8. Rory McIlroy
9. Brooks Koepka
10. Jason Day
11. Sergio Garcia 
12. Henrik Stenson 
13. Tommy Fleetwood 
14. Marc Leishman 
15. Tyrrell Hatton 
16. Alex Noren
17. Paul Casey
18. Pat Perez
19. Matt Kuchar
20. Brian Harman 
21. Rafael Cabrera Bello 
22. Francesco Molinari 
23. Charley Hoffman 
24. Patrick Reed
25. Xander Schauffele 
26. Ross Fisher 
27. Branden Grace 
28. Matthew Fitzpatrick 
29. Louis Oosthuizen 
30. Kevin Kisner 
31. Daniel Berger
32. Li Haotong
33. Kevin Chappell 
34. Thomas Pieters 
35. Satoshi Kodaira 
36. Patrick Cantlay 
37. Tony Finau
38. Charl Schwartzel 
39. Adam Scott 
40. Webb Simpson 
41. Jhonattan Vegas 
42. Siwoo Kim
43. Yuta Ikeda
44. Bernd Wiesberger 
45. Jason Dufner 
46. Kyle Stanley 
47. Dylan Frittelli 
48. Zach Johnson 
49. Phil Mickelson 
50. Russell Henley

Other Irish

• 67 Shane Lowry
• 76 Paul Dunne
• 163 Padraig Harrington 
• 209 Graeme McDowell 
• 311 Seamus Power
• 361 Gavin Moynihan
• 642 Michael Hoey
• 669 Jonathan Caldwell
• 840 Dermot McElroy 
• 926 Niall Kearney
• 977 Ruaidhri McGee
• 1076 Cormac Sharvin
• 1267 Brendan McCarroll
• 1321 Chris Selfridge
• 1347 Niall Turner
• 1381 Gary Hurley
• 1385 Rory McNamara
• 1385 Brian Casey
• 1410 Darren Clarke
• 1542 Tim Rice
• 1757 Damien McGrane 
• 1813 Kevin Phelan
• 1891 Stephen Grant
• 1914 David Carey