It's amazing how the Kings are 1st at defense with a player like Muzzin on the blueline. I really think a big reason why Doughty has struggled is that he is missing that Scuderi/O'Donnell type of defenseman, now he has to bail out his defense partner more often than not and has to cover for his mistakes.
I actually see why the coaching staff has no other option but to play Muzzin too. They really are lacking in depth on the blueline. Management retained Regehr because they knew Scuderi was going to walk away and Mitchell and Greene both practically missed an entire season due to injuries. So you have a combination of slow and beaten up veterans with inexperienced and mistake prone defensemen, and Drew Doughty who isn't playing his best hockey.
And despite all that, defense remains tops in the league, which goes to show you how much of a team effort it is, and for that reason, the offense struggles. The forwards are so focused in on supporting the defense combined with the struggles by the defensemen to get the puck up the ice and on the tapes of forwards' sticks are two magnifying reasons why this team just isn't getting it done on the scoreboard.