BROOKLINE, Mass. — Jon Rahm showed how quickly things could change at The Country Club by going from one ahead to one behind.

Before making a blunder on the final hole, the reigning champion appeared to be on his way to taking the 54-hole lead at the US Open. His double-bogey 6 dropped him to solo third, a shot behind Will Zalatoris and Matt Fitzpatrick, as he tries to become the seventh player to win the tournament back-to-back.

Rahm, known for his aggressive personality, was calm when he spoke with the media 15 minutes after his round.

"I'm quite happy, I'm not going to lie," Rahm said. "It's frustrating to finish that way considering how well I played those holes, but I kept telling myself that if you told me on the 14th hole that I could shoot one over par and skip the last five holes, I would have ran to the clubhouse because of how difficult it was playing." I would have accepted it without hesitation.

"I'll have to think about it." I have 18 holes left and am only one shot behind the leader. That's the crucial point."

Rahm had tumbled down the leaderboard and was two-over-par for the day when he arrived at the par-5 14th hole at Brookline on a cold, windswept day. He made a birdie there, then added another on 15 before closing with a birdie on 17 – his third in four holes – to take the lead at five-under.

However, much of his effort was wasted on the concluding hole. His tee shot landed in the left fairway bunker, and Rahm admitted that his 9-iron approach from the sand was "charming." His ball smashed onto the bunker's lip and almost rolled back to him.

"To be honest, it was a little dark and hard to see," Rahm remarked after finishing his round shortly before 8 p.m. local time. "I noticed the ball was a little bit deeper in the sand than I could see after hitting the shot."

Rahm then went bunker-to-bunker in the greenside sand, sketching a buried lie. He sliced out to 20 feet and bogeyed the putt for a 1-over 71.

"The truth is, it was six decent shots out of 18," he admitted. "Unfortunately, it totaled 6, but they were all good swings." As a result, I'm pleased in that regard."

Rahm will be in the final group, only one shot behind the leaders – a better position than he was in last year at Torrey Pines when he returned from a three-shot deficit to win his first major.

"I can't worry about it," Rahm said, one of nine players separated by only three shots. "I know someone in front of me will come out hot and score, and I know I'm going to have to play well and shoot in the red numbers." That is my responsibility.