I think it's a stretch to even call Cabrera average defensively. His range (which at the ML level is more important than having a good glove or arm) is truly horrific and by virtually every metric you can find, he's one of the worst third basemen in the league.
Even if he was above-average, his impact on the game defensively would still be dwarfed by Trout's. We're talking about the best CF in the AL and maybe all of baseball (don't watch enough NL to know for sure. I know Stubbs and Bourn are very well-regarded).