Jimmy Walker fired a 65 to lead the way on a weather-affected second day of the WGC-Bridgestone Invitational but had Thomas Pieters and Rory McIlroy breathing down his neck at Firestone Country Club.
After a 45-minute delay at the start of the day due to the threat of lightning, two further suspensions saw four hours and five minutes lost, with a spell of torrential rain in the early afternoon.
When the hooter sounded for the second time to spark a three hour and 19 minute delay, Walker and Pieters shared the lead at five under but the American picked up two birdies on the back nine to open up a two-shot advantage.
McIlroy was then in the group at four under after a 69, alongside World Number Three Hideki Matsuyama and 2015 Open champion Zach Johnson.
Russell Knox was a further shot back alongside Alex Noren, with Tommy Fleetwood then at two under.
Walker - who will defend his US PGA Championship title next week - has struggled this season after suffering with Lyme disease but showed all the qualities that made him a Major champion on Friday as he brushed off all the distractions to fire the lowest round of the day.
