The three-times major champion, who is riding a string of six consecutive top-10 finishes and had been installed as the favourite a week after a ninth place finish at Kapalua, declined to speak with the media following his round.
The duo began their 2018 seasons on Thursday on a mission to contend once again this week, carding seven-under 63s to share a one-stroke lead at the Sony Open in Hawaii. After dropping his lone shot from a bunker on the par-3 seventh, Harman hit 7-iron from 172 yards to 15 feet on the par-5 ninth for a closing eagle.
Johnson, victor of the 2007 Masters and the 2015 Open championship, broke away from the second-placed bunch at the final hole, despite finding a fairway bunker off the tee.
"I came here later than I anticipated -like four or five days later and I had zero expectations on my game", the 41-year-old said. "My swing kind of felt better and better as the day went on".
"I've probably been off long enough now that you never know what's going to happen", he said.
"I had a great day today, and I'm about to go do it".
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The birdie moved Kirk past Evans resident Vaughn Taylor, who had 64, as did former Clemson golfer Kyle Stanley and Talor Gooch.
Two-time major victor Johnson carded a bogey-free seven-under 63 in the afternoon wave that included a birdie at 18 to grab a share of the lead with early starter Kirk, who stormed into the clubhouse with four birdies over the final six holes. Harman, playing in the afternoon, had eight birdies that included three in a row at the fifth, sixth and seventh.
Spieth hit four trees with four shots on the par-4 eighth hole - his 17th of the opening round - starting with a tough break when his tee shot caromed off the trunk of a tree and down an 8-foot deep ditch that left him no good options.
Peter Malnati, Daisuke Kataoka, Matt Every and Tom Hoge opened with five-under 65s.
Thomas, who set the PGA Tour scoring record for 72 holes in his wire-to-wire victory, opened with a 67 and was all smiles at the end.
The Open champion birdied his final hole for a one-under-par 69 that left him tied for 65th on the Hawaiian island of Oahu, but it did little to ease the sting of the quadruple-bogey.