Knapp shot an 11-under 61 on Friday to break a Rocket Classic record that stood for less than a day and became the first on the tour to break 60 and shoot a 61 or lower in the same season.
But that still wasn't enough to put him in the top six, entering the weekend at Detroit Golf Club.
Chris Kirk (65), Philip Knowles (64) and Andrew Putnam (66) share the second-round lead at 14 under. Jackson Suber (65) was another shot back.
Aldrich Potgieter, who had a 70 after sharing the 18-hole lead with Kevin Roy after a record-setting 62, was two strokes back with Michael Thorbjornsen (67) and Mark Hubbard (69).
Knapp was in a large pack of players, including Australian Harrison Endycott (66), Collin Morikawa (64), Hideki Matsuyama (66) and Roy (71), three shots off the lead going into the third round.
Endycott followed his opening 67 with a bogey-free six-under 66. The 29-year-old Sydneysider made three birdies on each nine, including going back-to-back on 13 and 14.Â
The 31-year-old Knapp, who won the Mexico Open last year as a rookie, started the second round 130th in the 156-player field after opening with a 72. He surged into contention with nine birdies and an eagle in a bogey-free round.
"I was just probably upset all night and this morning, so I think that maybe helped a little bit," he said.
Knapp, ranked No.99 in the world, is the only player on the tour to shoot 61 or better in two rounds this season.
He shot a 59 - one off the tour scoring record of 58 set by Jim Furyk in 2016 - at the Cognizant Classic four months ago, when he broke the tournament scoring record before cooling off and tying for sixth.
Knapp broke the 18-hole record at Detroit Golf Club that was set Thursday in the first round when Potgieter and Roy both shot a 62.
"I feel like when I start making birdies, I want to make more," Knapp said. "I was even kind of thinking about 59 when I stuck it close on my third to last hole."
The 28-year-old Knowles, shooting for his first PGA Tour win, made the cut for just the third time in 11 events after failing to make it to the weekend at five straight tournaments.
"It's not been my best year thus far by any stretch of the imagination, but golf is funny," he said. "When you're playing bad, you never feel like you're going to play good again. And when you have days like today, you just don't understand how you could ever shoot a bad round of golf."
Min Woo Lee, the first to break the course record with a 63 on Thursday, made 73 on Friday to tumble down the field to tied 36th.
He made the six-under cut by two, but Aaron Baddeley (71,73), Cam Davis (74, 70) and Karl Vilips (71,74) will all miss the weekend action.
8°C