One of the biggest "Jeopardy!" champs of all time says the show is in good hands with Ken Jennings ... but he doesn't want Mayim Bialik to vanish completely.

We got Austin Rogers -- who went on a major hot streak in 2017 -- at Gaf East, a bar he just bought in New York City, and we asked him about Mayim announcing her exit as one of the "Jeopardy!" hosts.

Austin says the show will be just fine with Ken taking on an even larger role. Ken's become synonymous with "Jeopardy!" and AR feels he's a big enough name now to soften the blow of Mayim's departure.

Another "Jeopardy!" champ, Amy Schneider agrees ... telling us Ken is the right choice for the everyday hosting gig, in part because he's a big hit with the contestants.

While Mayim says Sony brass told her she won't be hosting the syndicated daily show, the studio is leaving the door open for her to host special episodes ... like "Celebrity Jeopardy" and other primetime tournaments -- and Austin explains why she's a good fit there.

TMZ broke the story ... Mayim's absence during the writers' strike made Sony execs realize they didn't need 2 hosts, and ultimately her loss was Ken's gain.

Austin says Mayim was still right to stand in solidarity with the writers, and he hopes she remains involved ... even if it's not on a daily basis.