It says a decent amount in context, especially in relationship to your team and teammates.
What it tells me is exactly what I see every time I see them play--he's an elite offensive defenseman that has defensive lapses aplenty.
Ottawa as a team is -12, so you wouldn't expect many of their players to be good there. However, Karlsson's usual partner is Methot, who is +6. His newest on and off partner is Claesson, so that hurts--and he's a -8. They're on a suck streak in that regard, so his is obviously dinged, but if you're going to call a guy the best all around d-man in the game, he can't be -1 when he has teammates (including d-men) that are +6, 5, 8, and 14 on the same team. And that's with his extremely offensive deployment (not tired from the PK--getting steadily fed 5v5 time and all the PP a guy can handle) so he's getting to pad his stats while getting the "boo hoo he's tired he can't be expected to carry his team defensively too" treatment from all the apologists.
To be fair I didn't see tonight's game so for all I know it's -3 the same way Doughty was vs. the first Ottawa game where McNabb ****ing fell down and a slowass changeup went thru Quick so who knows. All I know is that if you put up 47 points but you're still a 5v5 minus it's hard to argue you're having a statistically large positive impact on your team's chances to win despite being a high-CF% player. He still only has a 50% GF%, 8th on the Sens.
The thing is, those stats defy the eye test to a small degree, because I think he has a greater offensive impact than the points actually show--not in the sense that he should have more points, but that he's doing more throughout the game to generate offense (hence the high CF%). And he's usually decent defensively but he his breakdowns are so, so visible because they're judgment lapses and soft play in front of his own net, so honestly, he's like a microcosm of last year's Kings--drive play lots, but if you give up a chance, give up a gnarly one.
Not even going to dive deep into his GA and GA/60 again but he's still given up the most 5v5 goals in the league and his GA/60 is 167th out of 187 d-men who have played 300 or more minutes this year.
