Na felt such great control in Thursday's opening round that he matched his career low with a nine-under 61 and still found reason to be slightly disappointed when he walked off the Waialae course in Honolulu.
He had his sights on a sub-60 round, especially as the afternoon wind died, only to see three good birdie chances narrowly miss.
His 61 gave him only a one-shot lead over 51-year-old Jim Furyk and Russell Henley, with Kevin Chappell, Patton Kizire, Michael Thompson, Seamus Power and Haotong Li all a further shots back after 63s.
Perhaps unsurprisingly, Smith was unable to maintain the fierce pace he set when winning the Tournament of Champions at a tour-record 34 under par on Maui last week.
The Queenslander carded a 67 marred by two bogeys to be in a tie for 40th.
Cam Davis was the leading Australian after a 66 left him tied 24th.
March Leishman and Cameron Percy joined Smith a three under while Brett Drewitt was two under.
Like Smith, Matt Jones couldn't maintain the scoring that earned him third place last week with weekend rounds of 62 61. He shot an opening even par 70 on Thursday that was only good for tied 100th.
Na was bogey-free, and stress-free. All seven of his birdies and his eagle on the par-5 ninth hole were inside 10 feet.
Na now has five rounds at 61 in his PGA Tour career, including one in the third round on his way to victlory in the Sony Open last year.
"I did everything well today and my iron play was amazing," Na said. "And I tell you what, I had a chance for a 59. I gave it all I could. I'm a little disappointed my putts didn't fall, some of the good putts that I hit didn't fall."
Furyk is back in the hunt more than a quarter-century after he first won this tournament. He made a hole-in-one on the 17th hole to cap off a big run toward the end of his round.
Furyk went a decade without playing in Honolulu until returning last year once he became eligible for the 50-and-older PGA Tour Champions, which opens next week on the Big Island.
"Trying to get ready for this year and what do I look at this week? I want to be competitive," Furyk said.
Furyk won so long ago at Waialae that it was a year before Collin Morikawa was even born. The tournament had a different title sponsor in 1996, and the perks of winning ($US216,000 for first place, compared with $US1.35 million this year) included a United Airlines pass for two to travel anywhere in the world for a year.
There were other reminders for Furyk.
"Played a practice round with a guy that called me 'sir,' and later on he asked me what I liked most about the Champions Tour," Furyk said. "And I said, 'No one calls me 'sir.' He said his dad would be angry with him if he didn't."
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