TMZ Sports spoke with the wrestling legend about the ex-UFC star's upcoming fight with Lesnar at 'SmackDown' on Friday ... and we had to ask if Cain has a snowball's chance in hell at winning his first match.
"I'mma be real honest with you, I’ve been wrestling for 25 years, I have never seen a monster like Brock Lesner and the warpath that’s he’s been on for the past few years," Show tells us at LAX.
"He's stronger, he’s faster, he’s seasoned, he’s confident in where he is. He’s tough."
Big Show knows what he's talking about -- he's had several legendary matches against Lesnar in his career ... including SmackDown in 2003 when the freakin' RING COLLAPSED!!!
Of course, Cain and Lesnar met in the Octagon years ago, with Velasquez taking the win at UFC 121 ... but Big Show doesn't see history repeating itself.
As for critics of the matchup complaining about putting Cain against Brock in his first-ever WWE event, Show says people should just enjoy the fight for what it is.
"My first match was against Hulk Hogan for the World Championship. So, I can’t really throw that 'rushing' rock in a glass house, you know what I mean? If the opportunity knocks, take it. You can’t get mad at anyone who gets an opportunity and they take it."