Sammy Hagar had hoped his pal, Metallica frontman James Hetfield, would lay down vocals for this song as well, but it didn't work out. Hagar admitted to Rolling Stone: "I didn't really want to say this, but I'm completely honest: James Hetfield is a dear friend and we hang out in Hawaii a lot. Kid Rock did the duet on 'Knockdown Dragout,' which he recorded for me instantly. I would've just as soon had James Hetfield do it, but I ran into Kid, because I did that Detroit show with him, and we were communicating about other stuff and about his tour, so I just spontaneously asked him to sing on the track."
Hagar added, "And, boom, it got done. After he finished it, I thought that I would get James to sing just the 'Knockdown! Dragout!' part. I sent it to him and told him Kid Rock was on there and the whole thing, and he got back to me and said, quote-unquote, 'I'm completely flattered that you would want my sailor-assed voice on your record.' And then he said, '…but it isn't my style.' And I said, 'It's OK. I still love you, James.'"
"I really wanted him on there, but it doesn't fit," Hagar concluded. "I was cheating by sending him that song, because if he would've heard the whole album — if a Metallica fan would've heard this album and bought it because he was on there, they would be p----ed off. This isn't a Metallica record, you know? But he's my friend, and I would've loved to have had him on it."