That's what FS1's Rachel Bonnetta is bankin' on -- telling TMZ Sports the 43-year-old QB is the key to unlocking the grand prize in the big FOX Super 6 Super Bowl Contest ... despite being the "underdog."

The game is simple ... download the FOX Super 6 app (it's freeee!!!) and answer 6 questions correctly about how Super Bowl LV will shake out and you could win a quarter of a million bucks!!

One of the questions ... which team will win and by how many points?

Since Rachel deals with picking winners and losers every day on her show "Fox Bet Live," we hit her up for a little advice from a pro!!!

The good news ... Bonnetta has definitely done her research and fires off some solid well-researched tips.

The bad news ... there's no guarantee she's gonna be right!

So, check out the video ... make your best picks -- and CROSS YOUR FINGERS!!

Hey, the people at FOX Super 6 have already paid out more than $2 MILLION in winnings so far this NFL season ... why can't the next winner be you?!

And, if you're SUPER confident in your Super Bowl pics, you can put your money where your mouth is and place wagers on the FOX Bet Sportsbook app ... as long as you're 21 and live in Pennsylvania, NJ, Colorado and Michigan!

Good luck!

FOX Super 6: No purchase necessary. Open to legal residents of the US, excluding WA, 18 and older. See terms at foxsuper6.com.

Fox Bet Sportsbook: 21+ and present in NJ, PA, CO or MI.