Ex-Michigan State basketball star Mateen Cleaves says he DID have sex with the woman accusing him of rape ... but he's adamant the encounter was 100% consensual.
The 41-year-old -- who was the 14th overall pick in the 2000 NBA Draft -- appeared in court in Flint, Michigan for opening statements in his trial ... where he is facing multiple felony charges.
As we previously reported, the accuser claims Cleaves took her to a motel in 2015 and held her there against her will. She claims Cleaves forced himself on her and raped her.