"He didn't make any mistakes, and the birdies on 9 and 10 were big," Castro said after his 69.
The other leaders fell away. Andres Romero had a double bogey on the fourth hole and shot 75. James Driscoll didn't make a birdie in his round of 74.
Jordan Spieth, the 19-year-old from Texas who needs a win to become a PGA Tour member and be eligible for the FedEx Cup playoffs, started his day by holing out from a fairway bunker for eagle and chipping in for birdie to tie for the lead. He dropped a shot at No. 11 — the hardest hole at Congressional — about the time Haas was on his critical run of birdies. Spieth had a 69 and finished sixth, pushing his earnings for the year over $1.1 million.
D.H. Lee made nine birdies to match a tournament-best 64 and tied for third with Jason Kokrak, who briefly shared the lead on the front nine and had a 69. Stewart Cink closed with a 67 and finished alone in fifth, his best finish on the PGA Tour in stroke play since he won the British Open four years ago at Turnberry.
Haas made the long walk across a makeshift bridge and under the grandstands to the 18th green for the trophy presentation, high-fiving kids along the railing and raising his cap to thousands of fans who cheered as they saw him coming. His win was even sweeter when he compared it with all the times he failed.
"As many times as I've choked and hit bad shots and I've been nervous and it hasn't worked out — I was feeling all those things today — and to hit good, quality golf shots down the stretch is such a good feeling," Haas said. "I wish I could explain it. It's amazing."