I watched Yennaris in the flesh playing centre midfield for the England U19s at Brisbane Road last week - his work rate was a awesome (it really was), and he's a neat and tidy footballer, but there's no way he should be starting in midfield in a game like this.
If Song really is our only centre midfielder, then it seems obvious to me we go Song-Chamberlain in midfield, flanked by Walcott and Gervinho, with Robin and one of Chamkah or Park up front.
I really do hope we tear into them, regardless of the final outcome. The stuff about the pitch sounds like fighting talk from Wenger, he sounds up for it.