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Austin Rogers is freaking out over the stunning abilities of Ken Jennings, Brad Rutter and James Holzhauer ... the "Jeopardy!" sensation says these G.O.A.T.s are the LeBron's of trivia.

We got Austin -- who captivated America back in 2017 with an impressive 12-game winning streak on Alex Trebek's show -- in Harlem, and he couldn't stop gushing over the trio duking it out for a million-dollar prize.

Austin took home a whopping $411,000 during his run at the top, but he says he's been blown away watching Ken, Brad and James make some extremely difficult questions look like child's play ... and he's putting them on par with the greatest athletes on Earth.

As you know ... Ken's got the early lead after 3 games, and he needs one more victory to secure the cash and cement himself as the greatest "Jeopardy!" contestant ever. James has a win under his belt, and Brad's come up empty so far.

Austin says the tournament is far from over though ... he thinks Brad could be a spoiler, as long as one thing turns in his favor.