You also have to keep in mind that Tanev has sucked the past two years. His value is pretty much in the toilet.
Relative Corsi is -0.7 two years ago and -1.8 last year. That's not terrible, but it's nowhere what he used to be, and those numbers would be a lot worse if he was playing as many minutes a night as he used to. He could have very well been like Zaitsev last year with more injuries and less offense if he was playing in Zaitsev's role at those times.
His career average (including those two years) is +1.0, so he was pretty good before that, but his injuries plus poor play does not give him a ton of value (despite what Canucks fans may claim).
Brown + Nielsen + either Carrick or a heavily conditional pick that could be as high as a 2nd is the most he should be getting. If we lose Brown, then Hyman, Lindholm, Kapanen and Johnsson are probably the PKers and I guess Ennis would enter the lineup. Ennis would either not play on the special teams, or would replace Johnsson on the PP if Johnsson has to play too much PK in a game. Or maybe the Leafs will look at Winnik to play PK and on the 4th line. Although it would be a decent downgrade from Brown to Ennis/Winnik.