Its becoming difficult to believe your claim that you watched Herrera week in week out last year. Its very common knowledge that Valverde changed Bielsa's system. In fact, when the Herrera deal got made public, people on the caf were debating whether signing 'another number 10' was a good idea. The fact you claim Bilbao don't use attacking midfielders makes me wonder just how much you saw of them in 2013/14.
From what I have seen of Herrera I've every confidence he'll be a star for us once the Premier League begins. The claims you make about his sloppiness, as I said, I've never seen with my own eyes. Van Gaal has already declared that, along with Shinji and Mata, Herrera is the best passer at Man Utd. Given Van Gaal gave players like Xavi and Iniesta their debuts at Barcelona, I'd say the manager's a good judge of passing ability too.
Herrera takes risks with the ball but that's not a bad thing. Top class midfielders need to have courage, Gary Neville and Paul Scholes had a long discussion about this before and after we lost to City. Sometimes you need to have the guts to gamble if you're gonna win big. Herrera has
that in him and it will be a help not hinder United as we try to get back to where we belong: at the top of English football.