Inverness-born Knox is contesting the FedEx Cup Play-off Series for a first time in his short PGA Tour career and showed he wasn't fazed posting a four-under-par 67 in hot and humid conditions on the Ridgwood Country Club course in Paramus.
It put him into a clubhouse share of second place and just a shot behind the leading trio of Americans Charles Howell III, Cameron Tringale and Hunter Mahan.
Rory McIlroy, the world No.1 and currently leading the FedEx Cup standings, struggled his way around, though, shooting an indifferent three over par 74 that left him trailing in a share of 99th place.
Indeed, McIlroy struggled from the outset to be three over par after four holes, four over through nine and only ending his poor run ending by holing a 32-footer for birdie. It is the four-time major winner's poorest round since the 'Friday Fright' second-day 78 in last month's Scottish Open, a day after he had shot a then-Royal Aberdeen course record of 64.
"I actually felt I got off to a good start but just short-sided myself on the 12th - my third hole - and made double from there, and compounded it with a bogey at the next," said McIlroy. "I tried really hard to get some momentum going in the round but I just couldn't really do that."
McIlroy ruled out any suggestions of fatigue in the wake of his 'triple crown'-winning effort in capturing the Open Championship, the WGC-Bridgestone Invitational and the PGA Championship.
He spent three days after that latest triumph celebrating in nearby New York, was guest of honour at Saturday's Barclays Premier League opener at Old Trafford before jetting back to the Big Apple for corporate work, TV appearances and an ice bucket challenge with Tiger Woods.
"Yes, I've been to three, four, five - no four - different places, but it hasn't been too bad," he said. "I'm used to the travel; I'm used to doing that. It's nothing new to me. Fatigue isn't playing a part. It's just not putting time in that I probably should have over the past week [but] I allowed myself that and I deserved that. So I need to work hard on the range this afternoon and go out tomorrow and shoot a number."
Knox also started from the 10th and capped his round with four birdies from the 12th hole, the third of his day's work, although he singled out driving to the green at the fifth hole, his 14th, and then two-putting from 40 feet as the highlight of his first round at Ridgwood.
"It was a great start," he said. "This course is just a gem from the first tee to the 18th green; there were just so many holes that suited my eye. I played my front nine excellent; it was a good a nine holes I've played all season. I just kept [the ball] in play, made come great irons shots and holed some good putts.
"I didn't play the back nine as good but hung in there and not to drop a shot was very pleasing."
Knox recorded just 27 putts - that was five fewer than McIlroy - while he hit 11 of 14 fairways whereas the Northern Irishman struggled to hit even half. "Rory is just one player in the field I need to beat but I can't be focusing on finishing ahead of him because there is just so many amazing players here, and who have deserved to be here," said Knox. "[But] I have been waiting and looking forward all year to the play-offs as it was my goal at the start of the season. I'm not only comfortable playing this course but I feel really comfortable in these surroundings, playing the play-offs. I've had enough good finishes to feel as though I belong out here.
"Everyone starts from scratch this week so a good result here in New Jersey would take me on to Boston next week and then on to Denver and, hopefully, to the final event [the Tour Championship] in Atlanta and maybe get my hands on that $10m bonus . . . "