Historically, I have no idea.
I did manage to grab him off the wire in 3 dynasty leagues late last fall so I'm definately smoking the kool-aid on Allen. I have seen scouting reports that refer to him as a 'high motor' guy. I usually will take a chance on an obscure LB if he has the high motor tag. I hope he continues and builds off the success of his rookie season. The part that keeps my optimism grounded is that he is a
'lightly regarded DE ' from Idaho State. Seems to get by on guts and determination rather than talent. (although I didn't see much of him play last year) You may be right that 9 sacks is is maximum upside and its down hill from here. What worries me is what happens when OCs, who have had the spring to fully disect the 2004 season, begin to focus on Allen? What happens when he gets double teamed? KCs DLine is less than stellar so there is not protection of playing opposite a Peppers, Berry or Jason Taylor. He has Eric Hicks on the other side.
On the Chiefs site, it says he has been working to get more muscle mass. He seems like a hard worker so I'm giving him the benefit of the doubt that he will hit 10+ sacks. I know full well that I could be very wrong but I am not pinning my FF success on 10+ sacks from Allen. For a wire pick up, his upside out paces the risk.