If he needs SB, why is he trading away Weeks??
Also, I don't know if this is the same league you've posted other stuff about, but depending on the keeper settings, I don't know that I'd be sending away Jennings for this package. I love Fat Panda's prospect over the next few seasons, but Napoli doesn't really do it for me and I feel has a greater chance at finishing among the vast majority of the Catchers who don't suck than head and shoulders above them -- with the rigor of the position and what have you, nobody seems to be able to do it consistently (McCann would be the closest, for my money).
Anyway, moral of the story is, if I'm looking to trade Jennings who has an incredible amount of upside and potential, and has already shown some of it at the Major League level, it'd take more than a nice 3B (albeit the position is super thin), a Catcher who may or may not repeat last year's performance, and a SS who offers me speed in one of the worst lineups in baseball. If I'm trading Jennings, I'm getting a clear stud in return.