"I don't know how good of a judge I'd be. Although I am the only person that actually does what the contestants do as a performer, I'm not in that world," Connick said during a Thursday appearance on Idol host Ryan Seacrest's KISS-FM radio show.
"I can look at people objectively and say what I think about their performing skills or their singing skills -- that I know. But the pop world isn't my world, and this is a pop show."
Cowell's potential replacement has been a hot topic of conversation ever since he inked a January deal to leave American Idol this May and launch an American edition of his British The X Factor reality competition series on Fox in Fall 2011.
Connick said it was simply a "great, great honor" to serve as this past week's musical mentor and added he gained a new respect for the show's contestants.
"One reason I would have never made it on this show, I just was too cocky when I was that age," he told Seacrest. "I thought to be able to stand on that stage and basically face the whole country judging you -- I couldn't have done that. There's no way."
In addition, Connick -- who was also responsible for composing the arrangements of the songs the finalists sang and accompanied them on-stage with his big-band orchestra as they performed -- apologized to Shania Twain for comments he was shown making during a video package that aired at the beginning of Tuesday night's performance show.
"American Idol is keeping me pretty busy right now to be honest with you. I mean I should be out laying by the pool -- you think Shania Twain was up in here doing this?" he joked, referencing last week's Idol mentor.
Connick said American Idol producers "cut out" the actual joke he was trying to make.
"I tried to call Shania Twain because I said something that came across very insulting to her... What they cut out was, 'She's an A-list celebrity, she's probably at some huge party. They don't think of me like that so they lock me in the hotel room.' That was the joke. But it came across like, 'Shania's not up here doing all the work.' I'm like, 'Oh my god! They didn't put the funny part in!'" he told Seacrest.
"I felt so bad. I've got an email off to her as soon as I finish with you because if she saw it, she must think, 'What a loser? Why would he say that?'"