"I have not hit the ball as crisply the first two days (as) maybe some other tournaments this year, but I've probably putted the best of any tournament this year so far", Todd said. "The best players in the world treat each final round like it's just another day, and they just go out there and try to execute and stick to their game and let the results fall as they do".
But Koepka said he wasn't anxious with 36 holes remaining.
On the 406-yard par-4 12th, Fowler had a bogey after hitting the green in 3 and two putting, moving Fowler to 2 under for the round.
LPGA: Danielle Kang played bogey-free at Inverness Club for a 6-under 66 and a one-shot lead in the LPGA Drive On Championship in Toledo, Ohio.
Fowler then ended up in design with another not likely birdie from outdoors 40 feet, and he stated: "It's been good to see some putts enter, and these greens have to do with as excellent as they get". "It happened to just drift right there in the middle of the hole".
The 35-year-old American, who converted an impressive 50-foot birdie putt over a slope at the par-three 14th, walked off the course feeling better than ever heading into the weekend.
Fowler took the lead to himself for the first time when Todd bogeyed No. 10 to start the back nine.
Fourth-ranked Webb Simpson, another two-time victor this season, totaled 66 with four birdies on the back nine and is six strokes down in a tie for eighth with Jason Day of Australia, who had a 67, Louis Oosthuizen of South Africa, who also shot 67, and Sungjae Im of South Korea, who came in at 68. But Todd found the water just short of the green on the par-3 14th and threw his hat in disgust at his shot.
"I've had a little bit more consistency the last few weeks and this has been a good week so far", he added.
He has not finished lower than 12th between 2013 and 2018, including two runners-up and a third-place finish.
He made up for it with a 16-foot birdie putt on the par-5 No. 16 for a two-stroke lead again. But he couldn't get up and down from the rough off the fringe of the green on No. 17 for his fourth bogey. Jay Delsing first set the record in 1993 when this course was a par 71.
Phil Mickelson was one-over-par through three holes during the third round at the WGC FedEx St. Jude Invitational on Saturday but still felt inspired to send his brother and caddie a positive message.