Dustin Johnson took a two-shot lead in the Northern Trust at TPC Boston with a second-round 60.
Johnson fired five birdies and two eagles in an outward nine of 27 to place Jim Furyk's 58 at the 2016 Travelers Championship - the lowest score in PGA Tour history - under threat.
The 36-year-old picked up further shots at the 10th and 11th, but that was the end of the birdie blitz in the first FedEx Cup play-off event as his hopes of a sub-60 round disappeared.
Rory McIlroy and Tiger Woods both battled to make the cut at three under.
Woods bogeyed the fourth and 13th to leave him one short of the projected cut mark.
But he picked up birdies at the 14th and 15th and finished on three under after taking five at the par-four 17th.
McIlroy also finished on three under after birdies at the ninth, 13th and 16th.
It was an impressive response from the former world number one after dropped shots at the third, fifth, sixth and seventh had left him in real danger of missing the weekend.
Shane Lowry's two-under-par 69 left him two shots outside the cut line, while Graeme McDowell finished on seven over.
"I got off to a great start and through the first five or six holes I played really good, made some really nice putts," Johnson told Sky Sports.
"When I made the turn with birdies at 10 and 11, you're definitely thinking about shooting 59.
"I tried to keep playing one shot at a time, I knew I was swinging well so I just tried to keep giving myself looks.
"I had some looks coming down the stretch but I couldn't get one to go. But I'm still happy with the way I played and I'm in a good position leading into the weekend."
Former US Open champion Johnson would have become the 13th player to break 60 on the PGA Tour with a birdie at the 18th, but an errant drive cost him dear.
He had to lay up and his approach shot came up 15 feet short, with the birdie putt for 59 missing to the left.
Incredibly, Johnson's round was not the best of the day as his fellow American Scottie Scheffler carded 12 birdies and no bogeys on the par-71 layout.
Scheffler's 59 left him on 13 under par with Australian Cameron Davis and two behind halfway leader Johnson. It was the first time in PGA Tour history that two rounds of 60 or lower had been shot on the same day.
The 24-year-old from Texas, who finished in a tie for fourth in the US PGA Championship earlier this month, birdied the second, added four more in a row from the fourth and picked up another shot on the ninth to race to the turn in 30.
Further gains on the 10th, 11th, 14th, 15th and 16th left him needing to birdie the par-five 18th to break the 60 barrier and he calmly two-putted from around 80 feet from just short of the green.
Speaking after his round, Scheffler said: "I had some key up and downs at the beginning of the round that kind of got me rolling, freed me up a little bit.
"Then the momentum just kind of kept going. I never really lost momentum, which was nice."
England's Ian Poulter, in a tie for 12th, was the top European after he followed an opening-day 66 with a 67 to reach nine under, six shots back from Johnson.