Tom Brady's mentor and friend, Tom Martinez has died of a heart attack at age 66 on Wednesday.

The football guru died during a dialysis session, according to WVCB in Boston. Martinez, a retired football coach, had been awaiting a kidney transplant for two years but never found a successful donor. Martinez's doctors told him three months ago that he had mere months to live.

"I've been told I'm out of here, and I don't accept that," Martinez said in a past interview with ABC News in January. "I'm going to fight to the end."

His wife, Olivia, had dropped him off at the Satellite Dialysis Center in Redwood City, Calif., Wednesday for a routine appointment. She was called back after Martinez's heart attack claimed his life.

Martinez was determined to live, and his determination was also translated on the football field. "I tell the kids I don't care who it is, I don't care where we go, I don't care where we play, we don't whine about officials' calls, we don't whine about weather conditions," said Martinez to ABC last month. "You play hard and you play right to the end."

He coached football, women's basketball and softball at the College of San Mateo, where he won a combined 1,100 games. Known as "The Quarterback Whisperer," Martinez first met Brady when the future MVP was just 13. Brady signed up for Martinez's quarterback clinic and worked with the coach for the remainder of his career.

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"He's a great friend of mine for a very long time and taught me how to throw a football at a very young age," said Brady speaking to ABC News last month. "He's been looking for a kidney for quite awhile now."

Brady used his NFL fame to promote organ donation during the Super Bowl this year. Before the 2011 NFL season began, Brady visited his long-time mentor.

"He asked me to come out, right before the season started. Labor Day Weekend," Martinez told the Boston Herald last year. "He said he was off. His throwing was off. So I went out there Sunday, Monday, and Tuesday. We went through the film. Then all of a sudden, everything fell into place. Within about an hour, he was back to the old Tom Brady."

Martinez noted that he and Brady's session must have been effective. "Then he had that 517-yard game…I guess what we did worked," said the coach.