I remember his win from a (relatively select) bunch at Romandie in 2012. He's not explosive, no, but he does have the ability to put out a lot of power in an aero position -- such that no one was able to come round him on that day. Obviously, there's a big difference between a Romandie stage and the velodrome at Roubaix -- and I agree that his best option would be a solo attack -- but if the group's select enough to shed Greipel, Sagan and co, I'd at least be interested to see what happens.
(What I don't quite understand is why so many people are talking about him as a contender for PR. I mean: it would be massively impressive if he could do it, but so far he's only got a top-ten finish there, and the difference between that and winning is huge.)