What did you have a problem with specifically. I didn't think it was terrible. If anything I thought Mata should have been sent off.
I think my problem was consistency. The glaring one I remember was Mata got taken out, no foul. A very similar foul happens down the field on a Chicago player, yellow card. There weren't any game changing mistakes to really stew over. It can be fun to play the homer piling on the ref in the stadium, but overall I didn't think it was too bad given some of the strict calls we've seen lately.
The first half was just flat out bad. The second half got progressively better, especially as the substitutions were made.
The lineup was puzzling. Bravo (or a player like him) really needs to be in there to allow Pirlo to work, and I don't know how this should be a surprise at this point. It's not a crack on Pirlo, but his game has never been about putting in a defensive shift. The link between midfield and defense ostensibly should have gone through him, however without any other real distributive outlet (Saunders isn't going to long ball accurately to a forward) it was easy for Chicago to put pressure on him as Tommy Mac and Mix were further upfield. And when he had to break up Chicago's plays, he had no one to funnel the ball to start recycling possession. He resorted to Hollywood balls up to Mullins, who wasn't able to do much of anything all evening. This also led to a lot of passing along the back and some very uncomfortable moments with Saunders having the ball at his feet. A lot of the defensive hustle in midfield I felt was wasted, chicken-with-its-head-cut-off harrying rather than efficient reading of the game and blocking passing lanes. I thought when Bravo came on he did a good job of providing this cover.
Mendoza is turning into what I thought he'd be -- a lot of motor and not much else. It's exciting when he turns on the jets in space, but in a game when those moments are few and far between he either has to beat his man or get involved in build up play. Part of this, in his defense, is that he and Villa were so wide they were basically hugging the touchline (I'm assuming this was by instruction to try and stretch the field as much as possible) and Mullins had difficulty providing any viable holdup play to feed them.
I also thought Brillant had a pretty poor game. Yes, he won some arial battles, but he was also a part of some mind boggling giveaways. Lingered on the ball too much a few times and almost got caught out. This was more an issue in the first half than the second.
The WM formation had its faults, but I think it provides more balance with the personnel available than a 4-3-3 with a midfield of TMac, Mix, and Pirlo.
On a side note, I'm kind of starting to roll my eyes at the Poku and chicken bucket chants (except for the lady on the screen with one, that was hilarious).