TROON, Scotland — Jordan Spieth insisted the decision not to play golf in the Rio Olympics, which came only 24 hours earlier, was the hardest he has been forced to make in his young life.

“I can honestly say that,” the 22-year-old Spieth said Tuesday. “Harder than trying to decide what university to go to. Whether to turn professional and leave school. This was something I very much struggled with.”

He was at Troon, where the 145th British Open begins Thursday, at a news conference that typically would have dealt with his putting, his chances and his near-miss a year ago at St Andrews after wins in the Masters and U.S. Open.

But on Monday, at the last moment, Spieth announced that like three other top names on tour, Rory McIlroy, Jason Day and Dustin Johnson, he wouldn’t compete when golf returned to the Olympics for the first time in more than a century.

“Health concerns were my reason,” he said.

Spieth didn’t specifically mention the Zika virus, as did the other pros, but surely that mosquito-borne disease was primary.

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“Why was it so hard?” Spieth asked rhetorically of his reluctance to decide. “Because I’m a huge believer in Olympic golf. I’m a huge believer in playing for your country. I absolutely look forward to the Summer and Winter Olympics. It’s the most exciting sporting event for me to watch on TV, and to have a chance to be part of something I definitely look forward to trying to do.

“This year I just had to try and weigh a risk that doesn’t present itself every year. I just felt this was the right move for me. Not everybody’s going to understand that.”

What is understood is Spieth saying he would not enter the John Deere Classic. He has won the tournament twice in the previous three years, but in the mashed-up schedule of 2016 the Deere will be held opposite the Olympic tournament. “I don’t think,” Spieth said, “it would be appropriate to play that week.”

McIlroy, who followed Spieth’s interview, said he didn’t feel a responsibility to play in the Olympics to help spur the popularity of golf. It’s a sport in decline, particularly since the departure of Tiger Woods, who hasn’t played in a tournament in 11 months following back surgery.

“I don’t feel I’ve let the game down at all,” McIlroy said. “I didn’t get into golf to grow the game. I got into golf to win championships and win major championships, and all of a sudden there is a responsibility to grow the game.”

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McIlroy, who has won an Open, a U.S. Open and two PGA Championships, even took a bit of a swipe at the game. “I’ll probably watch the Olympics, but I’m not sure golf is one of the events I watch,’’ he said. “I’ll probably watch track and field, swimming, diving, the stuff that matters.”

Golf matters to Spieth.

“[The decision] will loom over me throughout the Olympic Games,” he said. “I will be, I’m sure, at times pretty upset that I’m not there. I thought about this ahead of time. When I watch the Opening Ceremonies, that’s going to be a big bummer. Then when I watch these guys competing on the golf course . . . ”

He’ll be home in Texas, wondering what might have been.