I would suggest you go to NHL.com and check Yandle's situational ice time from his rookie season on. If you think that it's just AV--it's not. Dave Tippett did his level best to keep Keith Yandle off his penalty killing unit. Why?
Anyway it's asinine to suggest that Yandle would be a better penalty killing defenseman than Girardi who has done it for years and much more often than not the Rangers in those years have had one of the best penalty killing units in the league.
Yandle is our best most instinctual and creative puck moving defenseman. My observation of him tells me that he's at the best when he has a bit of space to work with and at his worst when he's under heavy pressure. You can say that about practically every d-man but there are exceptions. Stralman was one and McDonagh is another. Any case Girardi is more able to handle the absorb the physical play that comes from playing lots of minutes on the PK. Yandle isn't.
And yet, you completely disregard the fact that he has, throughout his career not be tried there. You are also making an assumption that DT didn't play him there because he was bad at it. My guess would be, since Yandle was basically playing an average of 24 minutes a night over the course of the season, he needed to give him some minutes to rest. Obviously there's no debate that his offensive skills are in the elite level for D-Men (unless you're really dense). Maybe DT just wanted to utilize his Ice time in those situations rather than "wasting" him on the PK.
And herein lies the problem with AV. He doesn't give Yandle 24 minutes a night. In his short time last year he averaged just under 20 and this year he is averaging 1 second over 20. If you're not going to give Yandle those 4 extra minutes in offensive situations than he should be trying him on the PK.
My argument isn't "should Yandle be used on the PK" my argument is, it's possible he's not as potentially awful as everyone thinks, since frankly, we don't know.
I beleive and the metrics back my eye test up, that this team is better when Yandle is given more minutes. Unfortunately our moronic coach only does that when McD is out of the lineup. I don't think Yandle is a better overall D-Man than McD, but I also don't think it's as far off as many beleive. Yandle rarely plays in his own zone and that in and of itself is a form of defense. McD may be better at structural facets of defense but he plays in his own zone far more and is not nearly as effective when moving the puck (this isn't to say he isn't good--I think he is fantastic). If McD was at the level he was 2 seasons ago, I wouldn't be discussing this, but he hasn't been able to consistently play at that level again.
Regardless, this isn't about McD or Yandle. Obviously this team is strongest when both are in the lineup and utilized properly. However, our coach hasn't come close to doing that ths year.
And don't get me started on Girardi. He is horrendous as this point. Whether we're talking ES or PK. Yandle could be awful on the PK and still be nearly as effective as Girardi. His one skill is shot blocking and clearly that hasn't helped what has amounted to the worst season for our Pk in over a decade.