I wrote his bio for HF. I'll try not to repeat what's written there. I think his ceiling is a No. 2 defenseman. He's got all the talent to be a top pair defenseman, but most think that is a generous prediction. He handled being the top defenseman in Toronto quite well while he was there, so it wouldn't be new for him to be a top pair and relied on defenseman. I'd say he's close to an AHL contract (and if not he should be) because there isn't much left for him to learn after 4 solid OHL seasons. I'd expect him to play the entire year in the AHL next year then the following year spend the majority of the year in the AHL with a few possible call ups and after that, possibly a full timer.
I'm from Guelph, I've seen him play, he's a very good prospect, I'd say underrated as far as his HFs rating. Top four would be quite correct as long as there is nothing that goes wrong with his development...may need another year or two to get prepared.