I'm assuming you watched on TV and not at the ground? Kompany and Otamendi were absolutely superb, as was Yaya. It doesn't mean United had us under pressure, it means that United were playing on the break, but our two centre halves were imperious at cutting it out early and decisively.
Me and the guy I was at the game with both said DeBruyne was a major reason why we didn't break them down. United played 2 deep blocks and didn't allow him any space. So DeBruyne just disappeared for long spells and didn't offer himself as an option. He was supposed to be the playmaker. It's his job to constantly provide an option, and he completely failed at that.
Yaya had to step up to dictate play because DeBruyne was simply not interested in doing so. That led to Yaya having to spray 40 yard balls to the wingers, and Aguero having to drop 20 yards too deep to get the ball.
DeBruyne is fantastic when he's got loads of space to either run in to or exploit with one of his devastating early balls. But in tight spaces against deep lying packed defences, he's pretty uninterested and ineffective. A couple of decent crosses in a game isn't enough in that role. He should be dictating play in there, and he did a lousy job of that last night.