It is literally impossible to find up-to-date rankings of performance... the post I quoted was the best I could find.
That said, Nunes has game-by-game improved at RB. His forte is defense; he's not exceptional going forward.
His issues at RB have been:
1) Over-aggressive, needless challenges leading to free kicks after a foul and;
2) The occasional WTF! bone-head pass - as a RB - across the middle - or some such - leading to a goal scoring opportunity for the opposition.
Nunes is getting better and better at both 1 and 2 - and, for me at least - I have changed my opinion - I now like him as a starting RB in our side.
We can't be world best at every starting position - we need players that are solid and fit out style. Nunes has upped his game and is now good enough that I worry about who will start at RB if Nunes is injured.
Lest my take on Nunes seems completely stupid... there's posts aplenty about whether or not Nunes or Lewis was our first choice RB - some 2 months or so ago. I backed Nunes but felt that he wasn't up to the task as a first choice starter - I've now changed my mind and think that he's more than good enough as a starting RB... but... what if he's injured?