Tracy is accusing Tucker of making unwanted sexual comments and masturbating during an April 2022 phone call ... months after the two developed a personal friendship.

Tracy has since filed a Title IX complaint with the university ... detailing how the call resulted in her re-visiting her previous trauma.

Tucker was suspended without pay after the allegations went public ... and now, he's going scorched earth on Tracy and the investigation.

"Brenda Tracy's allegations of harassment are completely false," Tucker said in a lengthy statement. "The proceedings initiated by Ms. Tracy are devoid of any semblance of fairness for any matter of this importance, and the University's 'hearing' scheduled for October 5-6 is so flawed that there is no other opportunity for the truth to come out. That is why I share some truth with you now."

Tucker admits he developed an "intimate, adult relationship" with Tracy following her first visit to MSU in the summer of 2021 ... adding they would have late-night phone calls numerous times and disclose private information about each other, but noting she would initiate many of those conversations.

The coach -- who signed a huge, 10-year, $95 million deal in 2021 -- acknowledges the April 2022 call happened ... but said it was a "mutual, private event between two adults living at opposite ends of the country," and claims Tracy initiated the adult convo by making comments about what she would look like without clothes on.

Tucker claims Tracy welcomed their developed relationship ... requesting and accepting personal gifts, payments and donations to her non-profit. He also said Tracy went on to maintain communication with him, wishing him a happy Father's Day two months later.

Tucker also refutes Tracy's claim he canceled her scheduled appearance at the school following the phone call ... saying he was simply postponing it due to conflicts.

The most eye-opening part of Tucker's response, though, is when the coach suggests his potential firing could be used to make up for the school's mishandling of the Larry Nassar scandal.

"The investigation has not been fair or unbiased," Tucker continued. "I can only conclude that there is an ulterior motive designed to terminate my contract based on some other factor such as a desire to avoid any Nasser taint, or my race or gender."

He added ... "Ms. Tracy's attorney told us from the very beginning that I should not lose my job over her allegations, but that it would take a lot of money to make it go away. Her twisting of our personal relationship months after it concluded is designed to revive her career and destroy my life, precipitated by her greed."