It's an exaggeration to say he's built a really good squad of players. He has assembled a decent enough squad given the resources he has had, although you could argue that he has wasted a lot of time pursuing a "young and hungry" policy when he should have been mixing a few more experienced players into the squad, as he has now started to do.
For me, the really puzzling feature of his performance as a manager is his apparent tactical ineptitude. When he first came to the club, I was excited because I thought his tactical ability was one of his real strengths, but so many times we have seen puzzling selections, formations and styles of play. Yesterday was a good example. Defending so high up the pitch was a recipe for disaster against a side like Arsenal - how bizarre to let them score 5 times, all essentially from counterattacks! Also, although we had a good share of possession, the midfield spent a lot of time passing rather miserably to each other, with very little idea of how to get forward or run into space, as was rather well shown by the MOTD2 analysis last night.
Then there is a question about his understanding of what is going on, For him to say yesterday that "for 60 minutes or so we were in the game", and it "wasn't a 5-0 game" is worrying. We weren't ever really in the game, Paul, and it was a 5-0 game, indeed, we were lucky not to concede 6, 7, or even 8 as might have quite realistically happened.
And the scale of the defeat had much to do with your selections and tactics.
Source: Paul Lambert