Well, without a proper central midfield, we couldn't control the match and were more reliant on counters. It seemed pretty obvious that van Gaal wants to give everyone some match time and assess how well they understand the system and implement the philosophy.
Given how defensively weak our midfield was, our central defenders didn't do too badly. Smalling, particularly, was a very dominant defender and showed that he has the ability to play in defence for Man. Utd. He was stopping everything coming at him, and he played with so much confidence that I've never seen in him before. Blackett started to get unsettled and seemed to lose awareness of what was around him as he got under more pressure, and in a back 3, that's going to be troublesome particularly if we don't have a midfielder who's defensively solid. Michael Keane was very good in my opinion though started to fluster as we got under more pressure. Shaw still seems like he's getting used to the wing back role. Too often was he a bit too high, allowing for Roma's wing back to get in between him and Blackett into some good space. I'm not too worried about that, though. He'll settle into the system as he plays in it more often. Going forward, he wasn't too influential, but he played with more confidence and seemed more settled into the attacking side of the game.
Michael's brother, Will, was poor on the ball. His movement was good, and he has some nice upper-body strength, but playing in this system requires a forward who's good on the ball, which Will wasn't. He was poor at holding it up and lost it every time when running at the defenders. Chicharito didn't have much time to make an impact though he was good at linking up with the team and stretching Roma's defence. Lingard seemed to tire out and became less influential. It's clear he doesn't have it in him to play a more box-to-box role. Kagawa looked very promising as a #8 (more attacking central midfielder). He was very good at intercepting passes and winning the ball in midfield, and he was excellent in keeping the ball and playing it about at a fast pace. Nani was somewhat invisible, which isn't good for him. He doesn't look used to a forward role at all. Young was defensively poor, and I hope he never gets a match as a wing back again.
In terms of our team play, I'm very happy. We're moving the ball around at a much faster pace and playing at a quicker tempo than before. Our movement's much better, and the quick transitions are nice to see as well. van Gaal's really transformed our team, and I'm looking forward to us playing some very nice football.