Herschel Walker -- Considering MMA Fight ... At 53 Years Old

Age ain't nothin' but a number to Herschel Walker -- 'cause the NFL-turned-MMA-fighter tells TMZ Sports he's strongly considering getting back in the ring ... AT 53 YEARS OLD!!!!!

Walker is 2-0 is his MMA career ... but the last time he got in the ring was back in 2011 when he was 48.

Still, when we saw Walker in NYC yesterday, he assured us he's still training hard and staying in shape ... telling us when it comes to fighting again, "Don't rule it out! Herschel Walker may be fighting again soon."

#BadAss