SAN DIEGO — When Canada’s Mackenzie Hughes reached his tee shot on the par-3 11th hole in the final round of the 121st U.S. Open on Sunday, he couldn’t believe what he saw.

His ball was lodged between two twigs on the branch of a tree and never came down.

“I mean, it’s like one-in-a-million break,” Hughes said. “I’ve played golf my entire life, I’ve never had a ball stuck in a tree. For it to happen on the back nine of a U.S. Open …”

For more than two hours on Sunday, the back nine of the South Course at Torrey Pines chewed up many of the world’s best golfers and knocked most of them out of contention. In Hughes’ case, it didn’t even spit him out.

Before the leaders made the turn on Sunday, it seemed like one of the greatest final rounds in U.S. Open history was about to play out on the California coast. After six holes, four players — Louis Oosthuizen, Bryson DeChambeau, Russell Henley and Rory McIlroy — were tied for the lead at 4 under. Six more players, including Hughes, Brooks Koepka, Collin Morikawa and Jon Rahm, were just 1 shot behind.

“I’m not going to lie: I was trying not to look at the leaderboards, but the crowd was not cooperating,” Rahm said. “They were telling me exactly what was going on, so I decided to embrace it. You see all those great names, and to myself I thought whoever wins this one is going to be the one who won a U.S. Open with a star-packed leaderboard.”

But then, just as quickly, the U.S. Open resembled the final round of a local member-member.

“It’s late afternoon, Sunday at a U.S. Open,” said Harris English, who at one point was the clubhouse leader at 3-under. “The wind is up. The greens are firm and fast. Anything can happen.”

One by one, many of the best players in the world imploded, leaving Rahm chasing Oosthuizen for his first major championship. Rahm eventually chased the South African down to win by 1 shot at 6-under 278, becoming the first Spaniard to win the U.S. Open.

“You hear about many people saying all you need to do is just hang on and let others make mistakes, and that simply just wasn’t happening,” Rahm said.

Clearly, Rahm wasn’t paying much attention to the carnage that was happening everywhere around him.

Henley, who had at least a share of the lead after each of the first three rounds, took himself out of contention early with three straight bogeys. Justin Thomas, the No. 2 player in the world, was out of the mix after hitting his drive on No. 10 over a fence and out of bounds. Morikawa, the No. 4 player in the world, took a double bogey on No. 13 after blasting a wedge over the green. Koepka, a two-time U.S. Open champ, was undone by three back-nine bogeys.

Matthew Wolff, who was only 2 shots back at one point on Sunday, had bogeys on five of six holes to knock himself out. Northern Ireland’s Rory McIlroy, who was in contention for his first major championship win since the 2014 PGA Championship, three-putted No. 11 and made a double on 12.

“It was two holes that basically stopped the sort of run at the title,” McIlroy said.

Even after Oosthuizen had birdies on Nos. 9 and 10 to move to 6 under for a 2-shot lead, Hughes was still very much in the hunt at 4 under. But then he yanked his tee shot left on the par-3 11th. His ball narrowly missed a spectator and bounced high off the cart path. Unbelievably, the ball lodged in the tree and never came down.

Hughes took a penalty, made double-bogey 5 and then bogeyed the next hole. He was done, too.

“[It] felt unfortunate because if that ball is over there in the grass, I’ve got a chance to get up-and-down for par, and that’s a different outlook than trying to get up-and-down for bogey, and I ultimately made a double there,” Hughes said. “I hit a bad shot but I was left of the green with lots of green to work with, and who knows what would have happened. No, just a really bad break, and an unfortunate time to have it happen.”

That wasn’t even the strangest thing that happened. DeChambeau, who was cruising and hadn’t made a bogey in 30 consecutive holes, had back-to-back ones on Nos. 11 and 12. Then, after slipping on his tee shot on the par-5 13th, a fan wearing a cape ran onto the fairway ahead of him with a golf club. The man reached into his pocket, dropped a ball and knocked it into the canyon with an iron. He danced and swung again before police apprehended him.

“I’m just glad an officer clotheslined him,” DeChambeau said. “That was fun. They took him down and got him out like he should be.”

DeChambeau went down nearly as fast. The defending U.S. Open champion had held the solo lead at 5 under after a near-ace on the par-3 8th. After the consecutive bogeys, he took a double-bogey 7 on 13 and a quadruple-bogey 8 on 17. His bunker shot on the 13th ended up next to a 12-pack of beer near the cart path.

“Nobody understands, at least if you play professional golf, major championship golf,” DeChambeau said. “A lot of it is luck. I can’t tell you how many times I hit shots this week into bad lies and good lies, and they played out 50-50 this week. I caught the bad lies in the back nine [on Sunday]. … Had to be a little lucky. and I was for the first three and a half days and just didn’t get lucky on the last nine.”

No one knows that better than Hughes.