The 67-year-old was announced on Wednesday as Jeff Stelling's replacement on Channel 4's long-running gameshow.
Former OK! TV host Walsh told PA: "I think he'll be absolutely fantastic, I really love Nick.
"He's such a nice person and the faces he pulls - he looks like he's sucking on a lemon a lot of the time - but I think he'll make it really fun and bring a lot of new viewers to the show."
Lord Sugar's Apprentice aide has said: "I'm flattered to have been asked to present such an iconic programme and will work hard to justify sitting in the same seat as such great talents as Jeff Stelling, Des O'Connor and of course the great Richard Whiteley.
"It's particularly fitting that I should be doing this now as my spelling has started to slip quite badly. I used to be able to spell chrysanthemum."
His first episode as Countdown host will air on January 9, 2012.