Four-time PGA Tour winner Moore carded a bogey-free 67 on the challenging Innisbrook course to post a nine-under-par 204 total with one round left in Palm Harbor.

"I missed a lot of greens early. I hit some good chips and made a few great par-savers," Moore told NBC.

"But finally I got myself a couple of good birdie chances and was able to roll them in."

Spieth (68) wielded a hot putter, one-putting the final four greens to stand alone on eight-under, with compatriot Derek Ernst (69) in third place on seven-under.

Halfway leader Brendon de Jonge (75) frittered away his advantage with four consecutive bogeys from the sixth hole and ended the day seven shots behind.

Moore, ranked 32nd in the world, won the CIMB Classic, a PGA Tour event in Malaysia, in November and has carried his stellar form into 2015.

But nobody is hotter than Spieth, who won the Australian Open and then the Tiger Woods World Challenge in runaway fashion in back-to-back weeks late last year.

The 21-year-old nevertheless has only one PGA Tour victory to go with four runner-up finishes.

"I felt like I struck the ball well, not quite as nicely as the last couple of days, but my putter was there today," Spieth  said after sinking a six-foot putt to salvage par at the final hole.

"Those saves coming down the stretch were really big, one-putting the last four holes. That's going to do me a lot of good going into tomorrow, carry some confidence.

"Thursday I just didn't have the right speed. I left a lot of putts short and I've adjusted the last couple of days."

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