If he wasn't creative enough to be a no. 10, Brazil wouldn't play him there. It's not all about being the best attacker possible though, it's also about working within the system. For both club and country at the moment, Oscar is doing a very valuable job by harassing enemy midfielders and effectively turning their 4-2-3-1 into a more compact 4-3-3 when they don't have the ball. You only have to look at the 3-0 against Spain to see that in full effect. Mata can't do that.
If we going purely on creative ability, Mata is by far the superior choice and I don't see how anyone could possibly disagree with that. However, they perform different: Mata is the creative force, Oscar is the more rounded of the pair. You don't need to be an all out creator to play as an attacking midfielder, and to answer your question, yes he has got the skill to cut it there.
Different strokes for different folks and all that: Oscar is perfect for the top teams that rely on distribution from a deep midfield player, Mata for teams that need some magic to unlock them. So why we played Oscar at home vs Fulham is beyond me.