Martinez has battled a kidney condition for years, but the severity of his illness caught people by surprise over the weekend.
A melancholy Brady spoke with Sports Illustrated and described Martinez's influence over his career as "at the top of the list. Second to none."
Said Brady: "There is no one who knows more about throwing the football than (Martinez). And no one has meant more to me when it comes to throwing the football than Tom."
Brady told the publication that he met with Martinez for a passing session last Sunday.
"We spent two hours there (at an indoor facility in San Carlos, Calif.). He analyzed what I was doing, just like always. And when I got in the car with my dad afterward, I said to him, 'It's unbelievable how much he knows -- how much he helps me,'" Brady said.
"I just can't say enough about him, and what he's meant to me. When I heard how serious it was the other night, I was there in bed with my wife (Gisele Bündchen), and it was just a sad moment," Brady said. "Very tough on his family, and on ours."