Braun's UZR career for LF is -3.3, and for RF it's -7.6. Santana so far has a -11.8 UZR for his career in RF, and even worse elsewhere. Ryan Braun would probably be a slight upgrade defensively in RF, but considering he's getting older, not sure that it would be enough to make a playing time decision over. Just to add, Christian Yelich was 4.4 UZR in LF, and -5.9 in CF, and Lorenzo Cain is LF 13, CF 22.3, RF 14.5. The most consistent outfield defense would probably be Braun LF, Cain CF, Yelich RF, if you assume Yelich would end up somewhere between his LF and CF defensive rating. With the questions about his arm, it might be best to go with Yelich LF, Cain CF, and whoever in RF, and just try to roll the defense over towards RF more often than not to try to lessen the ground they have to cover over there. (This is purely from a defensive standpoint).