The Capitals just haven't been nearly as good at controlling play the past two seasons as they were prior to that. There are myriad reasons why but, based on how dramatically Semin's Relative Corsi rate has improved, I think we can conclude that Semin isn't one of those reasons. He's still driving play at an elite rate 5v5 compared to his teammates (significantly better than he used to, in fact) but since the team as a whole has struggled, that hasn't translated into as many opportunities as Semin was once getting.