MLB Manager Ron Washington -- I Cheated On My Wife ... That's Why I Quit

Former Texas Rangers manager Ron Washington is finally revealing why he quit the team -- saying, "I was not true to my wife after 42 years."

Washington left the team on Sept. 5th -- citing personal issues ... and hadn't elaborated on the nature of his issues until now.

But at a news conference in Dallas Thursday morning, Washington told reporters ... "I made a mistake, and I am embarrassed. I was not true to my wife after 42 years."

He continued, "I broke her trust. I am here today to own that mistake. All I ask is for your forgiveness and understanding."

Story developing ...