South Korea's Sung Kang powered into a commanding lead as a number of potential Masters contenders suffered an early exit from the Shell Houston Open.
Kang carded seven birdies and an eagle at the Golf Club of Houston to add a flawless 63 to his opening 65 and reach 16 under par, six shots clear of Americans Hudson Swafford and Russell Henley.
But at the other end of the leaderboard, former Masters winners Jordan Spieth and Adam Scott, 2016 runner-up Lee Westwood and Open champion Henrik Stenson all missed the halfway cut.
Kang began the day a shot behind overnight leader Rickie Fowler, but quickly erased that deficit with a birdie on the 11th, his second hole of the day.
Further birdies on the 15th and 17th took Kang to the turn in 33 and he picked up further shots on the first, second, fourth and seventh before holing from 30 feet for an eagle on the par-five eighth.
Kang is currently ranked 202nd in the world and had missed the cut in five of his nine PGA Tour events in 2017, but demonstrated he was capable of low scores with a second-round 60 in last year's AT&T Pebble Beach Pro-Am.
"I just putted a little better than yesterday, plus I was first off so the greens were really pure and I rolled it really nicely and they kept going in," Kang told Sky Sports 4.
A first PGA Tour victory on Sunday would also secure the final place in next week's Masters, but Kang added: "My experience is if I try to do something and think about the result it doesn't work out very well, so I'm taking it one shot at a time and the results will come."
Fowler could only add a 71 to his opening 64 to fall seven shots off the pace, with England's Justin Rose another three shots back after also returning a 71.
Spieth carded six bogeys and a solitary birdie in a disappointing 77, but insisted the poor weather forecast for the weekend in Houston did not make a missed cut any easier to swallow.
"No, because I was not playing this tournament just as a leeway into the Masters," Spieth told PGA Tour Live.
"I was playing this tournament because I love this tournament and we lost in a play-off here before. I know we can have success. The weather in Augusta is not good on Monday, either.
"I'm not sure what's going to happen with the end of this week into next week. Our plan is probably to get there by Saturday night or Sunday morning at this point and get to work."
Scott also shot 77 to finish one over par, with Westwood seven over after rounds of 77 and 74.