You'll remember ... the NFL superstar beat his then-4-year-old child with a switch so badly in 2014 -- the boy had bruises and lacerations on his lower back, buttocks and scrotum.

A.P. was charged with felony child abuse ... but was able to get that charge reduced to misdemeanor domestic violence after striking a plea deal in exchange for a no contest plea.

Peterson -- in addition to serving out a lengthy NFL suspension -- was sentenced to 80 hours of community service and ordered to pay a $4,000 fine.

Adrian said afterward he would find different ways to punish his kids, saying, "I won't ever use a switch again."

But ... fast forward to now -- and Peterson is singing a different tune, telling Bleacher Report he not only still uses a switch to discipline his kids sometimes ... he also recently used a belt too.

"I had to discipline my son and spank him the other day with a belt," Peterson said.

For his part ... A.P. says he doesn't take the punishments as far as he did back in 2014 -- claiming he uses the physical discipline only far enough to teach his children lessons he feels they need to learn.