(CNN) -- Tiger Woods faces two challengers as he bids to retain the world's No. 1 golf ranking for a 271st week at the WGC-Bridgestone Invitational starting in Ohio on Thursday.
The 34-year-old has been at the summit for an unprecedented 612 weeks in total, but once again faces the prospect of losing top spot to fellow American Phil Mickelson -- and a new contender, world No. 3 Lee Westwood.
While second-ranked Mickelson has failed to take advantage of Woods' struggles in recent weeks, finishing only tied for 48th at the British Open, Westwood has racked up the points after placing second at his home major last month.
The Englishman can go to No. 1 if he wins at Firestone and Woods is outside the top two -- or if he is second, the defending champion is 10th or lower and Mickelson does not win. CNN
