Well, I wouldn't say that we're learning that. Van Gaal knew that he needed to strengthen our defensive ranks, but he brought Rojo in and is very much trying to focus on bringing the youth team up and integrate them into the defence. I do understand that 'the best offence is a good defence', but with United, that's not really the case considering that we have the fire power up front, and to be honest after our last game against West Ham, I'm not so sure that we are lacking too badly in defence.
The goal was 100% de Gea's fault, he shouldn't have ran so far off the line for the ball during that corner, it was ridiculous. There were some very good clearances, McNair's header was absolutely amazing (not too mention pivotal) and Luke Shaw crossing over with di Maria was fantastic to watch. If anything, I think that our midfield and up front display suffered a lot more after Rooney was sent off.
Not looking forward to the next three games without him, though. We'll miss our captain, especially with Hererra gone in midfield with a fractured rib (I think that was it). He was easily one of the best players on the pitch last week.