A tumultuous day at the AT&T National ended with a four-way tie for the lead heading into Sunday's final round at Congressional Country Club in Bethesda, Maryland.
Roberto Castro chipped in from 80 feet after hitting his approach into the water to save par at the 18th and complete a 71 to join the group at seven-under-par 206 along with Andres Romero of Argentina, and Americans Bill Haas and James Driscoll.
Long-hitting Jason Kokrak, who powered a 349-yard drive at 18 on his way to finishing a 70 for 207, one stroke better than Tom Gillis and South Korea's Charlie Wi.
Wi made nine birdies, including seven on the front nine, on his way to a 65.
On a long, hot day for many players, who had to come in early on Saturday to finish their weather-interrupted second rounds, there were dramatic swings on the leaderboard at the long, rough-lined layout where numerous pins were placed on the edge of trouble.
Haas had nine birdies and only five pars in a three-under 68 that included a triple bogey and three other bogeys.
"Certainly, could have been a 6, 7, 8-under day," said Haas. "But it also could have been a 4, 5, 6-over day if I hadn't putted well."
"You can't blame being tired, it just was a long day and I didn't feel it with the golf swing. Luckily when I did hit a good shot, I was able to make a putt."
Jordan Spieth, a 19-year-old who began the round sharing the lead with Castro, took an early two-shot advantage after opening the round with two birdies to reach nine under par before he slipped back to four under, three strokes off the pace.
Romero, who had to finish five holes to complete his second round, made four birdies on the front side in the third round to climb to 10 under par and seize a three-stroke lead.
But the Argentine double-bogeyed the 11th, where Haas also tripled, and bogeyed the 12th to set up the logjam at the top as player fortunes rose and fell throughout the round.
Castro fell from the lead he had shared with Spieth heading into the round as he bogeyed the second hole and double-bogeyed the third.
But he worked his way back with four birdies, including ones at 16 and 17, as the leaders faltered to make it a foursome atop the leaderboard going to the final round.
Driscoll's round was relatively dull with five birdies and just two bogeys. He shot 68 and is the only player in the field with three rounds in the 60s.
"It's not perfect golf, but you don't really have to play perfect golf sometimes," Driscoll said.
"If you're just patient and putt well and have a good short game.
"There is no let-up. Every hole is long and tough. The rough is up. it's just 18 tough holes out there."
Because of a threat of poor weather on Sunday, players will again go off both tees in groups of three beginning at 8:30 a.m. ET with the final groups teeing off two hours later.