A healthy Livo is doing what he does well. JZ and Marquis are healthy. Picking up Gorzo was a nice move. A bottom of the rotation guy from a good team was going to be better than the AAAA fodder we were dealing with. No ace, but at least they're major-league caliber. Health is a big factor. Lannan's the weakest of the bunch, which was expected. Going from him being viewed as the best we have to a guy who is our number 5 is the big reason for the turn-around.
and that alone is while i may disagree with some of Rizzo's moves, I can't bash the guy - he took a team that featured JL as it's #1 starter and has built up the rotation to the point where Lannan is correctly in a #4 / #5 slot. The Marquis and Gorzo trades are probably the most important reasons why we're near .500 right now.