Note that you also commented on that same poster's suggestion back in June, in case that is what you were thinking of. Plouffe does't beat them by raw fWAR -- Lowrie and Valbuena combined for 7, versus Plouffe's 6.1. Plouffe does beat them in bWAR, although Lowrie logged most of his innings at short and DRS didn't care for his defense there. Of course, Plouffe has a WAR per PA advantage, but it's slight (roughly half a win over a full season) and almost all due to defense, further muddied by some positional differences (Valbuena and Lowrie haven't had anywhere near Plouffe's ample opportunity to become a competent defensive third baseman). Valbuena actually has more Rbat than Plouffe, in fewer PA the last two seasons. As you say, they have issues at first, probably in the outfield and catcher too, and most teams have some kind of issues on their pitching staff. I would be shocked if a speculative half-win defensive upgrade at third base would be any kind of priority for them. Which is probably why I can't find any such suggestion anywhere, except by one commenter at one site.