Purdy jumped 104 spots to come in at No. 69 this week, while O'Hair vaulted 228 positions to move into the top-100 at No. 96.
Tiger Woods saw his streak of 142 consecutive cuts made come to an end Friday at the Byron Nelson when he missed the weekend for the first time since 1998. Woods is still the top-ranked golfer this week, but Singh is right behind him and with both players out of action this week, Singh will become the No. 1 player in the world next week because Woods is scheduled to lose more points from his total according to the World Ranking's system.
Ernie Els, Phil Mickelson and Retief Goosen rounded out the 'Big Five.' Chris DiMarco was sixth, while Adam Scott, Sergio Garcia, Padraig Harrington and David Toms all held their positions from last week.
Luke Donald moved up one spot to No. 11, with Stewart Cink falling to No. 12. Darren Clarke was up to No. 13, while Mike Weir dropped to No. 14. Kenny Perry stayed put at No. 15, followed by Davis Love III, Stuart Appleby, Jim Furyk and Miguel Angel Jimenez.
Scott Verplank, who tied for sixth at the Byron Nelson, jump two spots to complete the top-20.
Thomas Bjorn won The Daily Telegraph Dunlop Masters in a playoff on Sunday and improved from No. 29 to No. 22 this week.