I'm with Pogue in terms of my perception of his performances thus far. Brilliant first game but in my opinion he's been pretty invisible ever since.
I have no doubts as to the lads ability, but he needs to tweak his game a little if he is to be more effective as a player in midfield - especially for ourselves. At the moment, I see a player who moves off the ball for moving off the balls sake far too much. Sometimes the best midfielders know when to just stay still and provide a better option for a pass whereas Herrera moves forward after laying it off every single time, which might draw attention but it means he is now in a difficult position to receive the pass again... which leads to the fluidity of the move being affected, with inevitable passes to the side or back to the centre-back. Basically he is making it hard for the likes of Fletcher etc to find him.
Another issue I have is his failure to make the ball 'stick'. Likes of Scholes and Xavi, hold on to that ball the right time before releasing, same goes for Pirlo... they don't ball hog, but they realise just by being on the ball... they're giving their team a lift and controlling the game. It also gives them more time to make a more meaningful pass.. but at the same time they have the ability to move it around quicker, just to mix it up and not get caught on it. Herrera in the first game - struck the right balance, but I've seen him a fair few times for Bilbao and his games v Roma/Inter.. where he just gets it and one touch passes it to someone else. It helps his passing %s look good, but in terms of him controlling the game, its useless if he is going to do that all the time... we need him to get on the ball and drive with it, making things happen.. not laying it off to the likes of Fletch and Clverely, forcing them to 'direct' the game. He needs to take responsibility and conduct the game.
Final issue, quality of passing.. he hits a brilliant through ball, but his mid range passing and long passing needs more work. I think it is linked with the problem of not holding onto the ball long enough, he rushes his passes. Slow the game down and he will make more accurate meaningful passes.