Omar Vizquel -- one of the greatest defensive shortstops ever -- is under MLB investigation over claims he beat his estranged wife ... but the ex-Cleveland superstar is flat-out denying the allegations.
According to The Athletic, Blanca Vizquel -- who married Omar in 2014 -- left the ex-baseball player in August and filed for divorce a short time later after she claims he was abusive toward her.
Blanca says the worst incident happened in 2016 ... claiming an argument escalated into a physical fight between the couple.
Blanca says she placed dumbbells behind a door to keep Omar away from her after the initial argument began .