Jonah Hill & Don Cheadle Watched Kevin Hart Box Poker Champ

Both Don Cheadle AND Jonah Hill showed up to watch Kevin Hart box a poker champ ... so says Antonio Esfandiari himself, who tells TMZ Sports his fight with the comedian was EPIC!!!

We spoke with 40-year-old Esfandiari just hours after Hart released footage of their scrap in Santa Monica earlier this month ... and he told us all about how he prepped for the fight.

After the battle, both fighters kept it professional -- giving props to each other for getting in the ring.

"It was by far the most challenging thing ever," Hart said ... "I gotta give [Antonio] credit because he didn’t let me fight the fight that I wanted to."

So, what's Antonio's breakdown of Hart's boxing game? Esfandiari tells us the little guy's got POP -- saying Kevin's right-hand carries KO power!!

As for the result ... Antonio won the fight via decision -- and ya gotta hear who he's thanking for the victory.