The University of Michigan is mourning the loss of athletics administrator Greg Harden, Tom Brady's life coach in Ann Arbor ... who died after complications from surgery.
The school shared the tragic news minutes ago ... days after it announced Harden remained in the hospital after undergoing a procedure on Monday.
Harden was known as the program's "secret weapon" due to his role as a mental coach for standout Wolverine athletes for decades ... including Brady, Desmond Howard, Jalen Rose and Michael Phelps.
Harden received credit for helping the university thrive in athletics since joining as a student-athlete counselor in 1986 ... and Brady previously praised him as one of the most influential people in his life.
"What I learned from Greg is still a part of who I am today," Brady said in a forward for Harden's book. "The world needs more Greg Hardens."
Brady also reacted to the loss on Friday ... saying, "I'm heartbroken as he was a dear friend and mentor. There are so many beautiful qualities Greg had that endeared him to so many people over his years at Michigan."
"He meant the world to me and I could never have had the success I had without the time, energy, love and support he had given me. He will be truly missed."
Howard added ... "Over the years, he positively impacted the lives of countless other student-athletes and their families. Greg brought wisdom, joy and his calming nature to every encounter. His presence will be missed by all of us."
Harden -- who was reportedly in his 70s -- is survived by his wife Shelia, sister Lynette and three children ... Brian, Victor and Olivia.
The family said it appreciates all the thoughts and prayers as they deal with the loss ... and will celebrate Harden's life at a ceremony in the future.