He's steady enough, but it's fecking annoying watching someone who was (one of) the best winger(s) in the league a few years ago to being so blunt even at right back where he has more time and space. Defensively he's good against kick and rush merchants, impenetrable even, but he's not a natural defender. I'm surprised Rafael can't get a look in, because he's not exactly setting the bar high.
For the "Fergie/Moyes/LvG loved him crew so he must be good" please note that neither Fergie or Moyes never played Valencia over Rafael at RB. They played him at RW, mainly because the other options were out of form Young and out of form, injured, lacking confidence (and a couple of years ago, almost out of contract) Nani. It's not like LvG hasn't made errors either (let's not start on 352 or Rooney in midfield...)