I cannot comment on Bumgarner or Drabek (not enough experience), but I would rate the other three as follows:
Garza: Dominating stuff. Gives up a few home runs, but he is a solid pitcher. His defense and a highly unlucky BABIP have led to his poor start. Definitely a huge buy low guy now.
Nolasco: He has shown great strike out potential over the past few years, but that high ERA is disturbing. Statistics say he has gotten unlucky with a very high BABIP, but after several years worth of data is it bad luck or the norm? His lower than normal strike out numbers so far this year have me alarmed, but I'm still waiting to hold court on him based on the potential he has shown over the years. If his BABIP goes down, his ERA will follow suit, and if he continues to accumulate K's he can be one of the more dominating pitchers in the league.
Kennedy: Has some nice quality pitches, but has not shown the ability to consistently fan batters. Also pitching for Arizona doesn't help. He's merely average at this point. If he develops more to his arsenal, he may be someone to watch in a few years, but nothing at this point makes him a great keeper.
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