17 July 2011 14:00 GMT

Darren Clarke still heads the Championship on five under par, but behind him everything is changing. The man to watch is Phil Mickelson, now just two shots behind and tied with Dustin Johnson in second place.

Mickelson birdied the second, the fiercely difficult fourth and the short sixth to bring him within two shots of the lead. His three at the 495-yard into-wind fourth was only the second sub-par score so far on the final day. The other was scored by Sergio Garcia.

Clarke holed what could prove a vitally important putt from 18 feet across the first green to save par. Had he missed, it might have set the wrong tone for his entire round. Faced with a six-footer for birdie at the next he stroked it firmly home, and had to do the same thing at the third to save par after racing his approach putt well past. These were the sort of putts that he missed by the handful yesterday and it will fill him with confidence to see them disappearing today. But he dropped a shot at the fourth and the in-form Mickleson is closing fast.

Rickie Fowler, in the glaring orange colours of Oklahoma State University, has opened with four straight pars and is fourth ahead of Thomas Bjorn who has dropped a shot.