I don't think anyone has ever questioned his quality, it's all about at what level that quality is. He's obviously a quality L1 player for example as all you need to do is, as you say look at his stats. The big question is can he do it consistently at a top champ team pushing for promotion and unfortunately the jury is still out on that for now.
Based on his performances so far (as ATM that's all we can go on), would you be happy if we paid £4m for him?
He's definitely improved over the last few games and hopefully that continues for us and him.