As we previously reported, the ex-Indians slugger was arrested for indecent exposure and DUI on Saturday after a woman told police Belle shook his genitals at her family -- including her 15-year-old daughter -- while urinating in the Phoenix Rising Soccer Club Stadium parking lot.

TMZ Sports spoke with Ron Swindells ... who says he was 15 feet away from Belle when he relieved himself and didn't see anything remotely close to that happen at any point.

Swindells tells us the woman making the claims was upset with the way he downplayed the situation ... yelling "are you effing kidding me?!" and Belle responded "Don't look, then. You gotta go, you gotta go."

We've obtained a picture of the alleged act ... showing the 51-year-old with his pants halfway down his legs, appearing to relieve himself while covering his body with the door of his car.

Swindells says Belle remained in that position while peeing and only turned his head to address the woman ... and is willing to speak to investigators about the incident.