Fantasy Baseball: Should I trade Hamels or Ervin Santana?

I'm giving Jose Reyes, Takeshi Saito, and either Cole Hamels or Ervin Santana....for Kelly Johnson, Jay Bruce, and Mariano Rivera. What do you guys think? Hamels' last start was horrible (gave up 7 runs, 3 homers) but many feel that overall he's one of the best pitchers in the game. Santana has been on fire for most of the season, so I'm not sure which one I want to offer.