The Arizona Diamondbacks have been getting production from unexpected sources, none more so than NL Player of the Month for March/April, Ildemaro Vargas . Vargas is currently batting .374 with a 1.041 OPS, six homers and 22 RBI At the same time, rookie Jose Fernandez came out of the gates hot, and despite cooling off the last couple of weeks, is still sporting a .304/.340/.435 batting line. His .775 OPS works out to a 114 OPS+, or about 14% better than league average. The return of Gabriel Moreno from the injured list has pushed catcher Adrian Del Castillo to the DH role, thus limiting the opportunity to get Fernandez into the lineup at DH the last couple of games. Things are about to get even more crowded. First baseman Carlos Santana's return from the injured list is imminent and creates an additional roster crunch . The question now becomes is if the veteran Santana plays with any regularity, who is he taking at bats away from?…