Do you think Walman is the best defensive dman in the NHL?
Of course not. I also haven't seen any actual advanced stats that suggest he is. The tweet is the
opinion that one specific website has reached from looking at their own proprietary algorithm that is not publicly available.
If you dig into the player card they made for Walman, you will see that he was in the 98th percentile for "Defense." This score appears to derive from his performance in the following categories: Defensive Impact (97th percentile), Denials (55th percentile), Recoveries (unscored), Role Difficulty (98th percentile), Penalties Taken (11th percentile), and Penalty Kill (52nd percentile). Each of these categories are defined in their glossary and utilizes advanced stats, but the way they plug the stats into their formula is hidden.
In other words, they take raw stats and plug them into their own (private) formula to determine how the player did in each category. They then put the results from those (private) formulas into another (private) formula to get a single total score. They then put the results onto easily digestible graphics they call player cards and hide everything except what they choose to tweet behind a paywall.
Their rankings are miles away from representing 'advanced stats' as a concept/tool.
I will note that the two areas he scored highly in happen to be the two areas they score that don't include any individual stats. The other 3 include individual stats (as well as on-ice stats) and see him drop way below those high-90th percentile scores.