So far during training camp, Tanev has shown a lot, from his relentlessness, tenaciousness and selflessness right down to his ability to tremendous character -- something Berube focused heavily on when responding to a question about his top defensive defenseman on Friday.
Time will ultimately tell whether the Tanev deal was a successful move or a costly mistake, but I'd be willing to wager that it's the former, rather than the latter, given what I've seen from him so far in camp. This decision has the potential to be a solid one for the Leafs.