4:46 PM PT -- Ryan Shazier tells TMZ ... "Michelle and I have been living apart and are currently separated. As we work through what comes next for our family, I ask for privacy and prayers."

Ryan Shazier is a "liar and a cheater" ... this according to his wife, who just put the former NFL linebacker on blast by sharing raunchy text messages she claims he sent to another woman.

Michelle Shazier -- who has been with Ryan well before his career-ending spinal cord injury in 2017 -- unleashed on her husband in a since-deleted Instagram post on Wednesday ... saying, "A person that loves his family … this is what they do to their family … the WIFE.. that has been there for him since day 1!"

Michelle -- a former college basketball player who has raised two boys with the Pro Bowler -- posted multiple text exchanges allegedly between Ryan and a woman named Marie ... and while they initially start off as casual flirting, things eventually got more intense.

In fact, in one screenshot, a text exchange shows the person Michelle claims is Ryan sending links to books titled "The Ultimate Guide To Anal Sex For Women" and "Blow By Blow: A Step-by-Step Guide On How To Give Blow Jobs So Explosive That He Will Be Willing To Do Anything For You."

"Infidelity at its finest!" Michelle continued in her post. "I can’t sit here and keep hiding anymore . You can have it. I deserve better. 🤍 This is Ryan… he’s a liar and a cheater!"

Ryan and Michelle got married back in May 2019. He has yet to address the allegations.