AP Photo/Charles Krupa

Some athletes skip the opening ceremony at the Olympics if they're competing the next day. American Jack Sock marched Friday night even though he was playing Saturday - and is suffering from walking pneumonia.

While several other tennis players ranked in the top 25 chose to skip the Rio Games, the 23-year-old Sock earlier this summer described the Olympics as something that’s on “the bucket list when you're a kid.”

So when he was diagnosed just before leaving for Rio de Janeiro, Sock explained Saturday, “I wasn’t going to take no for an answer.”

“I was going to come down and experience it no matter what,” he said.

What started as the common cold at the end of his run at Wimbledon in early July turned into a nagging cough that just wouldn’t go away. Sock, who was seeded 14th in Rio and is ranked 25th, finally went to his doctor the night before he departed and got a chest X-ray.

He feels fine when he’s not playing but struggled breathing at times in his 6-4, 6-4 loss to 118th-ranked Taro Daniel of Japan on Saturday. It was the first career win over a top-30 opponent for the 23-year-old U.S.-born Daniel.

“Obviously I wanted to do the best I could here,” Sock said, “but my expectations with this weren’t necessarily the highest.”

Former player and current commentator and coach Brad Gilbert seemed to believe that his expectations should have been a bit higher, resulting in a testy response from Sock.

Gilbert responded that he won bronze in his only Olympic appearance (in 1988), but he later tweeted that he hadn't been aware of Sock's illness and would "give myself a yellow card."

He tried to rest as much as possible upon arriving in Rio, but that wasn’t always doable as he found his way around at his first Olympics. And he wasn’t going to miss marching in the opening ceremony even though it meant he was up late Friday night.

The following afternoon, he had zero regrets.

“I thought it was the coolest thing I’ve ever been a part of,” Sock said. “It almost didn’t feel real. You walk out there and it was almost like a video game.”

Among his Olympic moments so far has been meeting golfer Rickie Fowler. Sock still plans to play in doubles with Steve Johnson and possibly mixed doubles.