As others have noted, Harrison is the real deal. He had several great crosses into the box, and one in particular that Villa probably should have put in the net. But the most impressive play I thought he had was around the 11-13'. He had the ball around midfield and dribbled out of trouble around 2-3 guys or so, made a run into the middle, then laid out a through ball releasing Mata wide. It was wonderful. It ended up not resulting in anything, but it was pure brilliance from Jack.
I actually thought Mena played decently. He had some shaky moments, but some of that I attribute to him not playing very much, especially with the group of guys that were on the field. His worst moments seemed to be receiving passes from our other guys, so perhaps moreso communication issues. But I thought he definitely showed what he is capable of physically and defensively.
As others have noted, Iraola is freeing Pirlo up massively. Pirlo had so much space yesterday and was able to play lots of great through balls to running teammates. He had a tremendous impact.
One other play I wanted to revisit was a chance off a shot Lampard had in the first half. I believe it was Mata who played a ball into the middle of the box to TMac with his back to goal, he spun onto his right foot and had plenty of space to shoot it, and was very surprised he didn't. The lay off to Lampard was a good play, but I thought he had a much better chance, turning onto his right foot, to put it in the net himself.