Kyle Seager didn't plan on opening up to a complete stranger about a part of his life he'd kept largely to himself.

The Mariners third baseman once wore T-shirts to the beach to hide the scar from the open heart surgery he'd had as a 5-month-old infant. He rarely volunteered information on it other than at checkups or when undergoing medical tests.

But last month, while Seager was warming up before a game for Seattle's Class AA affiliate in Jackson, Tenn., he couldn't keep quiet any longer. A stadium announcement told fans that an 11-year-old boy throwing out the ceremonial first pitch had a congenital heart problem known as Ventricular Septal Defect (VSD).

Seager knows all about VSD — a hole in the wall that separates the right and left ventricles of the heart. He'd been living with it his entire life. It's why he'd had surgery. And he knew right away what he had to do next.

"It was crazy because I was out there running my sprints and I could hear this thing on the speaker describing what he'd been through," Seager said. "He'd had the exact same surgery I did, was going through the exact same stuff." Seager had one thought: "I've got to go over there and say something."

William Witherspoon had just thrown out the first pitch when Seager jogged up to him.

"I got to talk to him for a little bit," said Seager, promoted to the majors twice since July only weeks after hitting .312 in AA. "We exchanged email addresses. It was crazy, somebody going through the exact same surgery. All the stuff he talks about that he has to do, all the doctors and everything and what they've said, it was exactly the same as what I did. I kind of just told him to keep his head up."

Seager didn't have anyone do that for him while growing up in North Carolina.

Doctors warned he couldn't play contact sports like football, so Seager stuck to baseball and soccer. Only as a teen was Seager told there was little risk the surgically repaired hole could be damaged by on-field trauma.

By then, Seager was in love with baseball and didn't want to change sports. Things are different with the boy.

"William just loves to play any kind of sport," the boy's mother, Season Witherspoon, said by phone from Tennessee of her football- and basketball-playing son, entering seventh grade. "He's so determined to play professional sports, but I'll tell you what, I think he'd do anything just to play in high school. He'd never met a professional athlete before and to have one come up to him and tell him he can do these things, it just meant the world to him."

Meeting Seager was the last thing young William expected when he went to the AA ballpark as part of an annual "Night of Heart" event held in conjunction with the American Heart Association.

He remembers what Seager first said: "I have the same heart problem as you."

"He told me I could do anything I wanted to with sports and not to let anybody tell me anything different," William Witherspoon recalled.

Seager's mother, Jody, was surprised Kyle opened up to a stranger.

"Kyle just never talks about it with anyone," she said. "So when I heard that he'd walked up to that little boy, I was just shocked. All through his life, it was something he had to deal with. But it was never something he talked about or wanted people to know about unless they had to."

Kyle was diagnosed with VSD when he was 2 weeks old, and doctors wanted to operate weeks later, his mother said. But they put it off for months because Kyle wasn't yet big enough.

The Seagers drove for 8 ½ hours to Birmingham, Ala., for the operation to seal the hole with a Gore-Tex patch. A second surgery cauterized some unexpected bleeding.

Jody watched her son closely for blue lips or other danger signs when he began playing non-contact sports.

Kyle Seager loved baseball from a young age, just like his college-playing dad, Jeff, and excelled at soccer, making an all-state Olympic development squad at age 12.

"He started playing so young and all that running they do just built his heart up strong," his mother said. "He'd go on the treadmill and he'd be above average."

Still, Seager was forced to constantly prove his heart wasn't a problem. At the University of North Carolina, he underwent tests every year, even though alum Brian Roberts, now a Baltimore Orioles infielder, had gone through something similar.

"Just to be sure," Seager said. "But there was never any problem."

The Mariners drafted Seager in the third round in 2009, then flew him to Seattle to sign his contract. But worried about what Seager called "a little heart murmur" he'd dealt with for years as a side issue, the team held off and flew him to Arizona.

"I was put on a machine and did a whole bunch of testing," Seager said. "Everything was fine, but it was just a big ordeal."

Seager admits he was "very self-conscious" about his scar growing up. Later, he'd simply say, "I had open heart surgery as a baby" when people asked. They'd usually leave it at that.

"I don't feel like I have to talk about it," he said. "It would be different if I had it when I was 12. But this has always been with me. I just accept it."

The team had doctors examine Seager before spring training. He figures that will continue the rest of his career, and the results will keep being normal.

"It's never stopped me from doing what I want to do and that's the important thing," he said.

Which is why Kyle Seager approached William Witherspoon before a game last month.

"That's what I wanted to let him know on the field that day," Seager said. "That you can still do anything you want to do."

Geoff Baker: 206-464-8286 or gbaker@seattletimes.com