He was electric in the big leagues — Rod Carew was a seven-time American League batting champ and earned 18 All-Star selections.

But after suffering a massive heart attack on a golf course in 2015, the Hall of Famer says some of his most important work now is off the field.

"I always felt like I was healthy, I never felt like anything was wrong with me. Until the morning that I had a massive heart attack. On the golf course, by myself," Carew said at a news conference Tuesday, part of an effort to convince more people to get their heart checked regularly and eat right.

Carew got a second chance at life in December when he got a heart transplant from another professional athlete: Konrad Reuland, a former NFL tight end who suffered a fatal brain aneurysm two days after Thanksgiving, and who in his final days also said he had more work to do.

"He wanted to always help other people and that's the way he lived his life," Reuland’s mother, Mary Reuland, said.

In April of 2016, Reuland made the decision in to be an organ donor while sitting at his mother’s California home and renewing his driver’s license.

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After the aneurysm was discovered and while Konrad was in the hospital, the former New York Jet and Baltimore Raven told his mother he was going to fight, and had more work to do. He underwent a 17-hour surgery but never came out of a coma.

"He’s completing his life that he started down here," Mary Reuland told NBC News Tuesday. "He told me while he was in the hospital, 'Mom I still have work to do' ... But I am now hopefully carrying it out, through him, through his guidance — and with the Carews."

Rod Carew holds Konrad Reuland's portrait as he stands for a photograph with Reuland's brother, Austin, left, their mother Mary and Carew's wife Rhonda in Encino, Calif. on April 18, 2017. Kort Waddell / NBC News

Now both families are hoping Konrad Reuland's legacy will be one of helping other families avoid heart disease — and that others sign up to be organ donors.

"I think my friend upstairs gave me another opportunity to continue his work. So that’s why I was left behind. I’ve got a great partner in Konrad," Carew said. "You know, he's given me a strong heart. You know, every day the doctors came in and they would say, 'boy he's roaring today.'"

Carew, who spent most of his career with the Minnesota Twins but also played for the team formerly known as the California Angels, was inducted into the Hall of Fame in 1991. He had a career average of .328 and 3,053 hits over the span of a nearly two-decade career, according to the hall of fame.

Konrad Reuland, who stood 6-foot 4 and 260 pounds, finished his college career at Stanford University, was signed by the San Francisco 49ers in 2011 and went on to play for the Jets for two seasons and played for the Ravens in the 2015 season.

The Carew and Reuland families have become close thanks to Konrad’s life-saving gift.

"When I left him for the last time I told the doctors, I said: 'I hope that whoever gets his heart better deserve it, because it was a good heart.' And I really feel that the man that got his heart truly did deserve it,” Mary Reuland said.

"I feel that in some divine way Konrad is up there directing where his parts went. His kidney went to somebody wonderful as well, and I’m sure his liver did too," she said. "So he saved some more people."

On the last day she was with Konrad, Mary Reuland laid her head to her son’s chest to hear his heartbeat "from morning until night, when I had to leave him.”

And she got a chance to hear her son’s heart beat again, through Carew.

"It was miraculous. It was just a wonderful thing to be able to hear a part of my son still here on earth," she said.