It's more down to Valverde's system. Arthur is more like Xavi than anyone. Xavi was generally played alongside Iniesta or another more attacking midfielder like Cesc. Valverde is basically asking Arthur to play like Iniesta when he's not that type of player. If you want to see the best out of Arthur you can't pair him with Vidal. Against teams that press like Spurs and Madrid he has looked phenomenal even alongside Rakitic, but I think he will be even better if he is allowed to be the main 6, taking over Rakitic's place eventually. If you look at Pep's City, they are generally playing with a midfield 3 of Fernandinho - KDB - Silva, with Gundogan rotating through. I would like to see Valverde experiment with a more attacking midfield and using Alena or maybe Coutinho in that role, but he is a pragmatic manager so we won't see that.