Zach Johnson made a good start to move within two shots of halfway leader Padraig Harrington in Ohio as the World Golf Championships-Bridgestone Invitational third round got under way.
Following an opening 64, Harrington had exercised caution on Friday as he held onto his lead with a 69 on a course that had begun to firm up after heavy rain in the previous week.
The reigning US PGA champion, though, said he would need to be more aggressive in his third round with Tim Clark breathing down his neck and a string of top-ranked players within six shots of his lead.
Rain had began to fall at Firestone for the first time in the tournament with thunderstorms also forecast for later in the day as Harrington and South Africa’s Clark teed off in the final pairing.
By then former Masters Tournament winner Johnson had picked up a couple of shots to go to five under for the week through two holes.
Australians Nick O'Hern and Robert Allenby each moved to four under par, three off the lead. O'Hern birdied the first three holes and had not dropped a shot after five, while Allenby birdied his opening hole.