They got us a couple times late with that action where they ran a high PNR, and then screened Mark when he stayed in drop coverage. That was what led to the wide open Walker three - it wasn't that Mark was just playing off him, it was that he didn't think they'd switched.
I will say, for as much as I adore Mark and think he's the only guy on the team that consistently plays like a pro, he seems to struggle in PNR coverage. I'm sure some of it is scheme and coaching, and some of it is our guards (esp. Moore) not doing a great job of fighting over screens and staying in the play, but Mark often seems a step slow to diagnose what's going on and decisively communicate the plan to the other defender. The net result when that happens is a guard completely picked off by a screen and out of the play, and Mark caught in no man's land in drop coverage trying to defend a 2-on-1 like 15 feet from the rim.
It's weird - we mostly run drop coverage these days, and occasionally ice side ballscreens, which is great, in theory. But unlike 4-5 years ago, when we first switched to those two strategies from the halfcourt hedge, it seems very haphazard, random and reactive, rather than intentional and aggressive. I'm not sure how much of that is on Mark vs just not having it be as much of an area of focus anymore.