Kevin Shattenkirk is a very good defenseman. In fact, one could easily make an argument he's the best the St. Louis Blues have.
So when a player of that caliber says defending against certain opponents is tough, you believe him. And as he told Craig Custance on ESPN.com: defending against Patrick Kane and Artemi Panarin is tough:
When you watch them, they're always within 10 or 15 feet of each other. When one guy has the puck in the neutral zone, the other guy is rushing over, not necessarily to get in the offensive zone right away but to support each other and create odd-man opportunities. That's what they do so well ... they move away from the puck.
The reason it's so tough is because it causes confusion on who is covering who, when they're crossing.
So how is Shattenkirk supposed to defend against two of the most potent weapons the entire NHL has to offer? Kane was a challenge in and of himself, but Panarin makes it a whole new game.
So his strategy? He has to pick his spots, and disrupt their game as best he can:
You have to be in their face as much as possible, not allow that to happen, not allow them to get as close to each other and support each other. When you can't, you have to be patient, sit back and almost let those crosses and misdirections happen and trust you're in a good position.
There's no doubt the Blues are going to be narrowed in on Kane and Panarin. Good luck to them, though - because teams have had to deal with them all season long, and it hasn't been an issue.
The Blues have gotten physical against the Blackhawks in past playoff series; but Chicago has won all of the recent ones, and they didn't even have Panarin then. Now? Well, the task just got that much tougher for Shattenkirk and the Blues. They may know what they have to do - but that doesn't mean they'll be able to do it.