I disagree. Although it's a shame that the player we have now barely resembles that monstrous winger we used to have, he's been reliable and a pretty consistent performer while playing right back this year for me. Rafa should start every game and it's one of the issues I have with van Gaal that he doesn't get a look-in but I find that hard to hold against Valencia.
He hasn't been particularly bad, sure, but I just don't think he's been anything really.
Recently I've started to really look at what players genuinely add to the team. And Valencia in any position, IMO, simply fills a gap. He does it, usually, without doing anything too terrible and he is consistent in that. Thats not what I want personally. I want players that can contribute to the kind of football that we want. A RB needs to be solid in defence, but also needs to be able to contribute well with going forward too. Valencia just seems to be there without ever really offering anything.
That being said, there are probably more important areas to sort out first, so long as performances like tonight aren't a regular thing.