Atlanta Braves outfielder Ronald Acuña Jr. was accosted out of nowhere by a couple of fans ... getting knocked to the ground during his team's Monday night game against the Colorado Rockies.
The bizarre incident went down in the 7th inning at Denver's Coors Field when one fan dashed into the outfield and gave Acuña a huge hug.
Check out the video ... the hugger won't let go of Acuña as security guards run up to them and try to break it up.
Eventually, the guards pull the dude off Acuña .