Thought Clev played well yest. If he can stay fit then I think he'll slot in well. Only issue is how much he'll be able to actually pass and move which a lot of his game seems to be based on. GB didn't exactly keep possession amazingly well and a better team would probably exposed the space that the likes of Clev were leaving with their game plan. Carrick's a better holding player though so that will help and if Clev can striker up a good balance with Kagawa ahead of him then could work well.
As for signing a midfielder, I've said before if everyone is fit, from a creative issue I don't see much wrong. Because of our style we don't need a massively creative centre, we really just need two balanced players in there. We've not really had a chance to see that with injuries. Now we can hope that clev and ando stay fit, and in scholes, giggs, powell there is, even if not ideal, cover. Personally I'm happy to given them one more season to prove they can stay fit and then have an impact.
However as I've said before we have no cover, other than a sick Fletcher for Carrick. If he get's injured then personally I think europe and the league are out of the question. The job carrick provides is just too important given the weaknesses virtually all our midfielders have. Maybe you could get away with Ando and Clev as a partnership provided they're fit at the same time, but personally I think it would be as open as it was last season. But if one of them is out then that means you're looking at clev/ando partnering a scholes, giggs or powell or potentially Jones, if they're both out...it's not good. That to me is a midfield with obvious weaknesses and without getting lucky will get exposed. We need cover for Carrick and in some games, games where we want to be defensively solid, someone who can come in alongside him to give that that. It's something we lack and without it, it will make rotating very difficult and risky and simply make the threat of injury a big problem. It's not unreasonable to expect that Carrick might not be fit for everygame, or available, so having an alternative for the most important role in our midfield, for me is something we can't avoid.