"A lot of people expect the right hand of Jake Paul to be this devastating punch," Hasim says. "I try to tell people he can't punch, but don't listen to me."

Remember, Hasim and Jake were supposed to cut the trash talk and fight for real on Aug. 6 ... but the bout was canceled due to a weight issue (although Rahman believes Jake purposely scrapped it out of fear).

Paul ended up taking on Anderson Silva -- and WINNING -- on Oct. 29 ... and Rahman tells us Spider committed the blunder of squaring up, a common mistake MMA fighters commit since they aren't used to boxing.

"He didn't hurt him when he knocked him down," Hasim says. "Anderson became square which means his legs were parallel, and he had no balance to catch himself from being hit."

"I think if he landed that same punch and Andersons not square," he added. "I highly doubt Anderson would've went down."

"Saying that, from the beginning, I think that Jake never really wanted to be in the ring with me," Rahman tells us. "I think he's a duck," he added.

Despite all that happened with Paul, Rahman tells us his focus is on his upcoming fight on Nov. 19 against Vitor Belfort in Texas -- and not on Jake, or his older brother, Logan, who he calls a "bigger b****."

"These guys have let the internet convince them in their minds that they are who they aren't," Rahman says. "We call them keyboard warriors. We still waiting on Logan to get a win."

"If Logan can go ahead and actually win a fight, we'll be in good business but until then, they really just keyboard warriors to me."