Mike Richards -- who infamously lost the "Jeopardy!" hosting gig after one day due to old controversial comments he'd made -- told People that the NFL star was a frontrunner for the job after impressing as a guest host on the trivia show.

As Mike puts it ... Aaron was the most prepared guest host -- which is saying something since he guest hosted alongside TV pros like Anderson Cooper, Bill Whitaker, Savannah Guthrie, George Stephanopoulos, LeVar Burton, and Robin Roberts, among other notable names.

But, according to MR, Aaron prepped for the show very intensely and was still lovely to everyone on the staff. So, the professional quarterback was seriously considered to replace Alex -- and he was apparently interested, too.

When asked how he would juggle both hosting duties and football, Aaron supposedly told Mike that the "Jeopardy!" team would figure it out.

Alas, the job ultimately went to Mike ... who was eventually replaced by famed "Jeopardy!" champ Ken Jennings and actress Mayim Bialik after his swift firing. A less surprising contender was Katie Couric, who Mike says brought a different look to the quiz show.

On the issue of his infamous exit from the show ... Mike notes that a lot of half-truths led to his exile from the entertainment industry. For starters, he defends that he did not pick himself for the highly sought-after gig -- a panel selected him for the role in 2021.