Yup, it was answered during a post game or practice media scrum. I remember him stating that there are several situations where it is helpful to have two forwards out on the ice who can take draws. He also mentioned that he wanted the team to spend less time out on the perimeter and that taking one of the big bodies out of the lineup frustrated that goal. Blash also mentioned that there were a lot of other good things that he was doing even though he wasn't scoring.
Riley obviously isn't anything special as a player, but he has been working hard over the last twenty or so games and has always been a responsible, coach's player. Like it or not he is still more skilled with the puck than Ott, Glendening and Helm (probably Abby too). Sadly, he never really overcame his skating issues and it greatly limits the manner in which he can play at this level and his overall effectiveness. What we are witnessing is a player who cannot really create his own offense and really depends on his line mates for offensive production.
More skilled how? You know who has a ton of skill? Tomas Jurco. A good lot it has done him without the brain to go with it. And Jurco hasn't had near the god-given minutes, linemates, and NHL debut timing that Sheahan has had.
Sheahan is not as skilled as Helm and Abby. Does he have a better shot? Yes. Pulkkinen's is better. That's where his advantage ends. He can't distribute pucks well when under pressure. He loses pucks easily after winning a battle. Unless he is a ball joint of a center between two skilled wingers, he has no idea where to be without the puck in the offensive zone. And he knows ****-all about getting a shot off. He has the brain, confidence, and physicality of Ville Leino, and his production will never look better than average without the most opportune of circumstances, much like Leino himself.
If you want to argue about the definition of skills, then you can run with that semantic argument, but at the end of the day, his tools + IQ pale in comparison to the tools + IQ of Abby and Helm.
And the worst part is, his brain and confidence are even holding him back from being an effective grinder. For all that should be in his favor, he comes out slightly above average in the defensive realm, despite being accepted and groomed as such for effectively two years running now.
That said, he still should be in the lineup. Through rote familiarity, anyone can learn to be effective in a role if given enough time, and the organization is clearly willing to give him that (as would most be, I'd imagine). The big issue now is figuring out where he needs to be and sticking with it.