DENVER -- Rockies third baseman Nolan Arenado and Sam Grayston, 17, of Laguna Hills, Calif., have this way of pleasantly surprising each other.

Saturday afternoon was Grayston’s turn.

Grayston hasn’t let cystic fibrosis -- a progressive, genetic disease that causes persistent lung infections and constricts the ability to breathe over time -- prevent him from becoming a solid high school first baseman. And when the Make-A-Wish Foundation asked Grayston what his wish was, he said it was to visit Coors Field, hang out with the Rockies and take batting practice with his favorite player.

So the Rockies simply approached Arenado about hosting a Make-A-Wish trip. Then they revealed who was making the trip.

“Hey, I know that kid,” a surprised Arenado said.

But that was nothing compared to when Arenado surprised Grayston.

A couple winters ago, Arenado needed to do some fielding drills on a rainy day. Since his usual workout place had a grass field, Arenado called Drew Hillman, a former high school teammate who had become coach at Laguna Hills High -- site of a turf field.

So Hillman asked Grayston, who was diagnosed at birth and had 40 percent of his small intestine surgically removed, to catch throws from “his friend.”

Arenado showed up.

“Drew told one of his guys to come catch for me, and Sam came out,” Arenado said. “I would always be like, ‘Drew, should I give him a little money because he’s taking care of me?’ He said, ‘No, just give him a pair of batting gloves or something.’

“This offseason and the one before, he would come catch and work with me, and I got to know him.”

Grayston, who will be a senior next season as a first baseman and pitcher and would love to earn a college scholarship, is like many baseball fans in admiring Arenado. But they don’t get on the field with a six-time Rawlings Gold Glove Award winner. It has happened four times over the last two offseasons.

“It’s still pretty surreal,” Grayston said. “My coach invited me down there. He didn’t tell me who was going to be there. He just said, ‘I need a first baseman to field for me.’”

So, what is it like to be on the business end of throws from simply one of the greatest third basemen of any era?

“It’s something you’ve got to experience first-hand,” Grayston said. “Somebody who is able to throw on the run, or not even looking, and still hit you in the chest, that’s something that’s still hard to comprehend when you’re there. He goes all out.”

Grayston and his family experienced all-out hospitality from the Rockies. And Grayston showed a little of what he could do. While taking regular batting practice with a group preparing to play the Dodgers, Grayston -- using a wood bat like the pros and wearing a Rockies No. 11 jersey -- lined several pitches to the warning track with an easy swing.

Laurie Grayston, who was at Coors with Sam, his older brother Jack and their dad Joe, said Sam is doing his breathing treatments and taking enzymes and medications daily, but the condition doesn’t consume the family. There is too much baseball being discussed to obsess about that.

Joe Grayston played at Azuza Pacific and was a 15th-round Draft pick of the Rangers in 1984. His career ended after two seasons because of a rotator-cuff injury. Joe Grayston became a Los Angeles County firefighter.

And Mom enjoyed Sam's expression.

“He’s just been speechless,” Laurie Grayston said. “He’s trying to play it cool, but he just can’t wipe that smile off his face.”

Learn more about Sam's Make-A-Wish journey in mid-July as part of the "My Wish" series on ESPN.