I'd rather take that risk on another game. The thing with this one is that it's our first against a quality team that's winning and playing well. The media will be all over it and, even if you ignore the media, winning is vital for our confidence and momentum.I think generally speaking Lucas acts as the central defender when attacking, but you're right, there's not much pace at the back. But I think it's a risk worth taking for the team to really develop its attacking game.
It's certainly not the team for Arsenal. I think Enrique's still out, Coutinho's likely going to get knackered quickly (he's not the most blessed with stamina as it is) so with the current personnel I'd hope the 3-5-2 is kept.
With current personnel, no matter who is coming back from injury, our best players should play. Our best players are those with the form, match fitness and playing in the right position.