Errol Spence Tells the World Why Shawn Porter Could Upset Him

Errol Spence says anyone who thinks Shawn Porter can't beat him is DEAD wrong ... 'cause Spence says Showtime definitely has what it takes to pull the upset.

Porter is a heavy betting underdog in the fight this weekend -- even though Shawn is an elite fighter himself -- and current WBC Welterweight champion.

Most think Spence is too big and skilled to lose the fight, but when we talked to Errol he told us he's not even listening to that talk ... cause he knows how good Porter is.

"This is a huge fight. He has the pedigree to upset me if I'm not on pinpoint and I'm not sharp and I'm not accurate. Me, I'm going to stay focused and not care about the odds."

Those odds are pretty lopsided -- you have to bet $800 on Errol just to win $100 -- but Spence says being the favorite hasn't changed his process.

"I'm 100% focused on the hunt."

Errol has another reason to lock in as well ... he's eyeing a big-money match-up with Manny Pacquiao down the line.

But, lose Saturday, that $100 million fight goes up in smoke.

No pressure though, right???

We also talked to Porter ... and no surprise, he also believes he can beat Spence. In fact, he says it's a 100% lock he wins.