I had a feeling that Carlson would get more ice time when the Caps are trailing, skewing his numbers positively. I did an Alzner WOWY, but limited my dataset to score-tied Corsi events only.
Link. I removed all players with whom Alzner did not have at least 100 Corsi events with. That got rid of every defenseman except for Carlson. Yeah, you could say they played together a lot.
Looking at their numbers breakdown (which I linked to above), with the two separated, Alzner probably faced tougher competition than Carlson, and with worse zone starts than Carlson. Yet, the only Corsi% advantage Carlson could muster (with a small sample size caveat) was only 2.2%.
Even if I bought it earlier, it's fair to say Carlson was not carrying Alzner. In fact, I'm not even so sure Carlson is a better even strength defenseman anymore. He has more scoring ability, but Alzner looks just as capable of tilting the ice in the Caps' favor.
Note how much better Bradley, Hendricks, Gordon, and Steckel were (with the score tied) with Alzner on the ice. Wow. Granted, they probably faced harder zone starts, but also lesser competition. I hope Green/Wideman-Hamrlik can provide similar support to their forwards.