Ex-MLB pitcher Matt Mantei was convicted of domestic violence after roughing up his wife, but he ain't gonna spend a minute behind bars ... TMZ Sports has learned.
We broke the story ... Mantei -- who was known for his 100 MPH heater during his 10-year career in the big leagues -- was arrested April 17 in Michigan after his wife told cops Mantei got physical with her while arguing over a cell phone.
She claimed the closer grabbed her, threw her to the floor, and held her down .