Steve Nash, Allen Iverson, Andre Iguodala, Josh Smith, and Shaquile O'Neal.
That's a solid B-list All-Star team, right? Imagine if they all got together on one team. No one would look forward to going up against that squad, regardless of who lines the bench on that team.
Now imagine going up against that lineup every game. You're probably not going to win a lot of games facing a roster that loaded night in and night out. Yet, according to 82games' opponents production by position, that's essentially what the Wizards are going up against every night. When you take the opposing PER of each position and compare it with the player at each position with the closest PER, you get the lineup that I just mentioned.
PG: 17.2 - Steve Nash (17.0)
SG: 18.3 - Allen Iverson (18.4)
SF: 14.3 - Andre Iguodala (14.4)
PF: 16.6 - Josh Smith (16.6)
C: 22.6 - Shaquile O'Neal (22.7)
For comparison's sake, here's the lineup that the Lakers (currently have the top defense in the NBA) would have to face if they faced the player with the closest PER to their opponents average production.
PG: 19.4 - Jose Calderon (20.1)
SG: 8.8 - Raja Bell (8.7)
SF: 12.9 - Luol Deng (12.9)
PF: 11.7 - Ryan Gomes (11.4)
C: 13.1 - Tyson Chandler (13.0)
With all due respect to the five players just listed, that squad would have no chance against the team that the Wizards have to go up against every night. When you have to match All-Star level numbers at nearly every position because of your inability to defend, you need to play nearly a perfect game every night to have a chance to win. Whereas when you face that second lineup, you can survive an off shooting night because you're defense lets you play a weaker lineup on a nightly basis.
If you're looking for a reason why the Lakers are 10-1 and the Wizards are 1-10, it all comes down to the lineups they play every night.