Rod Carew received a heart and kidney transplant in December. USATSI

Hall of Famer Rod Carew underwent a successful heart and kidney transplant in Los Angeles in December. Carew, now 71, had been using a mechanical device to pump blood following a massive heart attack in September 2015.

According to Garrett Downing, the heart and kidney Carew received came from former NFL player Konrad Reuland. Reuland, who played for four teams during his career, died at 29 due to a brain aneurysm in December. Coincidentally, Reuland and Carew met years earlier, when Reuland was 11.

Here's more from Downing:

Unbeknownst to Carew, Konrad Reuland, a little boy he had met nearly 20 years earlier, died three days later.

Two days after that, Carew received the call he had been waiting for – he would be getting a new heart and kidney. He underwent a 13-hour procedure to receive the transplants.

The surgery was a success, and the Carews were eternally grateful to the man whose heart and kidney Rod had received. Rod's wife, Rhonda, had friends who had seen the news of Reuland's death and asked her if that was the heart he received, but they had no way of knowing.

The Carews initially had no information about the donor other than the man's age. But that detail alone was enough to leave them in awe. Rod's campaign to fight heart disease was called the Heart of 29, in honor of the number he wore throughout his baseball career.

They didn't know it at the time, but he had, in fact, received the heart of 29-year-old Konrad.

The Reuland family was initially unaware of who received their son's heart and kidney. It wasn't until weeks later that Reuland's mother Mary was able to connect the dots, and later confirm her son's heart and kidney had indeed gone to Carew.

This is believed to be the first organ transplant between two professional athletes.