The former Take That star – who will perform his new single Bodies on Sunday’s results show – apparently admitted that he was no match for this year’s hopefuls.
“I would definitely have entered The X Factor if I was a kid now,” he said. “Of course I would have.
“I’d be excited and overwhelmed by the opportunity of getting through one of the rounds. It would be the only format to do that for someone like me.
“My voice isn’t as good as some of these people competing,” he added. “I might not have got through because I am lucky if I can get through a song and I’ve sung it in key. These people can really sing.”
Williams will act as a mentor to the 12 acts in the live finals this weekend, but said he had no idea what advice to give them.
“I’ve got to go and do mentoring and I haven’t got a clue what I am going to say,” he admitted.
“I wouldn’t know what to tell myself. If there are little nuances that need to be changed in the music and the way they are singing, I am not going to spot them.”
Girl group Kandy Rain are the bookies’ favourites to be the first act eliminated from the live shows.
Paddy Power are offering odds of 13-8 on the quartet getting the boot this weekend, with twins John and Edward second favourites at 7-4.
Welsh singer Lucie Jones is currently the bookies’ favourite to win the series, followed by teacher Danyl Johnson.