Hopefully this is the last post I have on this subject for a while.
I think it's a bit reductive to try and define good defensive play in black-and-white terms. Most people look at guys who block shots, throw checks, and find other ways to be useful away from the puck, and obviously players who cause turnovers either by an active stick or using their body. And FTR I'm not about to discount those factors, they're all important, even shot blocking.
But I think there's more to it than that. There's those forwards who work hard down low, assist the defense in battles for the puck, and are very adept at puck retrieval. I'm listening to a podcast now featuring Rachel Doerrie and Ian "Graph" Tulloch and both of them looooooove the moves the Avs made. She's very emphatic about the puck retrieval skills that Joonas Donskoi has. I'd argue Alex Kerfoot also has very good puck retrieval skills, which is a big reason behind those amazing zone exit numbers. He can get to loose pucks and skate them out of danger, but he also works hard to get to those pucks. That, to me, is a vital trait to have, especially when Colorado simply didn't have a lot of guys who could do that. Surely some of you see the logic in a big guy like Z knocking someone off the puck, and a guy like Kerf taking the resulting turnover and skating it out. Not everyone can do that.
I also absolutely think that those of you who think Kerf is "soft" are out to lunch. He's not. He was more than willing to skate into the dirty areas along the boards and in front of the net and battle for pucks. He may not have had the size to knock people around but I don't think that is the end-all-be-all of a good defensive player.
So I'll conclude with this: Alex Kerfoot is a very good defensive forward. Not elite, but very good. His offense is decent, and he provided an invaluable asset by being a guy who could assist the defense (especially guys like EJ and Z who can get stuck in their own zone) and retrieve pucks to skate them out of trouble. They needed that because they did not have the depth on the back end or up front. Now they do, and arguably they may have a better version of Kerfoot in Joonas Donskoi who is big, fast, more experienced, and also drives play and is very good defensively. He too is very good at puck retrieval and is able to skate it out of the zone, though he is not quite as good in that one specific trait as Kerfoot (at least last time I checked). Regardless, the Avs have acquired the depth and puckmoving ability that should allow them to improve defensively and make themselves an even more formidable offensive force. Kerf was a very good stopgap measure that shouldn't be needed any longer. I think he'll do well in Toronto.