Well that is certainly not true. Ander was significantly better than Marouane this season, or the last. Love how after a couple of weeks out, we're downgrading his performances. Infact Herrera has been one of the Top 20 players in the league so far performance wise, and is on numerous team of the season watch-lists.
Ander was more creative, more productive scoring 2 goals, had a better passing rate, played more decisive passes, won back more possession, was disciplined less often, had more open play dribbles etc etc and was better statistically :
Dunno how anyone can claim otherwise. Another thing to note, is that since Ander been injured, our style of play has regressed, and our most important player thus far - Di Maria has been forced wide to accommodate others rendering him subpar, instead of the #8 he's so effective at. Can't wait till Herrera makes a comeback following full recovery. Not only has he been better despite coming into a new league but he has much higher upside.