Day defeated Victor Dubuisson on the 23rd hole Sunday for the Match Play title. It was his second PGA win and fifth professional win overall. His other PGA victory came in May 2010 at the HP Byron Nelson Championship.
He goes from 11th to No. 4 in this week's rankings, knocking a series of seven players each down one place. Matt Kuchar leaves the Top 10 and is 11th.
Dubuisson also improves seven places to No. 23 in the rankings.
The rankings continue to be led by Tiger Woods, who returns to tournament play this week at the PGA's Honda Classic in Florida. Woods has been No. 1 for a total of 671 weeks.
The European Tour is back after a week off with the Tshwane Open in South Africa.
The men's world golf rankings WTA Top 10, listing player's name, home country and rankings points average:
1. Tiger Woods, United States, 10.27
2. Adam Scott, Australia, 8.79
3. Henrik Stenson, Sweden, 8.47
4. Jason Day, Australia, 6.94
5. Phil Mickelson, United States, 6.76
6. Justin Rose, England, 6.34
7. Zach Johnson, United States, 6.03
8. Rory McIlroy, Northern Ireland, 6.00
9. Sergio Garcia, Spain, 5.91
10. Dustin Johnson, United States, 5.78