Sorry, but the bit about Wenger and inheriting a defence is nonsense. From his best ever side "the invincibles", he only inherited Ashley Cole out of his entire back first choice back four. Even then, he was the manager who gave Cole his debut. Sol Campbell, Kolo Toure and Lauren were all brought in by Wenger.
They all played alongside and with Adams, Keown, they came to Arsenal and had someone OTHER than Wenger telling them what to do, where to be, Adams organised that defence, even when he wasn't in it, those players benefited from every day they trained or played games with Adams and Keown in the team.
Adams played for not far off 20 years, he was the captain for over a dozen years IIRC, he was there for a full season with Campbell/Kolo before he retired, training with the team, teaching them the ropes, Lauren had been with Adams and Cole for 2-3 years, Keown was there for donkeys years.
Wenger did inherit the defence, but the leadership and the training as well, the guy who in training tells his left back and right back where the hell to be. When he retired after the 01/02 season, Campbell, Lauren, Cole, Keown, Gio and Kolo had all played a minimum of one season with him, had trained with him, several of those Keown, Lauren and Cole had multiple seasons with him.
Don't forget that Keown was a top defender and was training with Arsenal at the same time as Adam's as a youngster before he left for several seasons, he was there till, 2004.
By the end of 2006, it was basically Kolo left who had played any serious number of games with Adams or Keown, and how long as the team been going downhill, particularly defensively. Gallas is a top player, and was an awesome partnership along with Terry, but who was the captain.
Arsenal lacked a leading defender, a real captain, and lacked someone to take charge in games and most likely in training. Since Kolo/Gallas left, the team has entirely fallen apart defensively with absolutely zero cohesion, no sense, completely disorganised.
THere is more to a team than a name on the sheet. Adams stops playing at one point, his influence on the team doesn't. The team up till 2004 had serious leadership, immense mental strength, discipline and quality players. By 2006 a huge portion of players who ever played in part of Keown and/or Adams defence were gone. The continuing year on year drop in quality defensively is clear as day, and when it started was particularly obvious.
Now, Adams was a player you can't simply expect to replace. But isn't it funny that in the run to a champs league final, Cygan, Senderos, Flamini and Lauren played a huge part?
What do Cygan, Senderos, Lauren and Flamini have in common, are they individually better than Clichy, Gallas, Vermaelen, Sagna, only Lauren was better than Sagna.
The difference is the worse players were part of a better trained, better drilled, better organised defence, players who had played with Keown, Adams, Campbell multiple times. The better players lacked playing with organisation, a leader, or any guidance/tactics/good training.
What is the difference then, groups of better players can't do as well as a rag tag makeshift defence in 04/05 who set champions league defensive records.... Wenger was there the whole time, the players improved but the defence is worse.
Teams are FAR more than the influence of just the CURRENT manager. THe players, the type of players, the leadership and the previous managers work are all part of any current team. Honestly unless you get a Wenger or Fergie and see how the team is donkeys years down the line after they've changed everyone and you can really see a team based purely on that manager, its impossible to say exactly how good any manager is.