speaking in general, "sloppy seconds" is when your friend/a guy you know dumps his girlfriend/a potential hook up and you jump right on that. It would make sense if we were picking 5th, 4th, even 2nd overall (if you really hate Cam and just one team turning him down is enough for someone to make this joke) and nobody ahead of us picked him, or, metaphorically, dumped/turned him down, but seeing as how the first team that got the chance to draft Cam picked him (us), he's not sloppy seconds.
"sloppy seconds" would more accurately describe what happens when a QB on a team fails to live up to expectations, is not retained or resigned, and gets picked up/signed by another team.
Haha oh is that what it means?
Maybe I'll stick with tongue punching the hot girls fat friend's fart box analogy then.