This is a really difficult question. By the japanese baseball book I would say the one that have the highest chance to contact, so maybe it's... Pedroia (I don't know the statistics of who's the best in this one).
The 4th should be the power hitter, the big bat, so I would choose A-gon.
But, It's kind hard to come up with a solution, as the american style of baseball just hates to do smallball tactics, like bunt or sacrifice...
Me, personally, I would put Ellsbury and Crawford and probably Pedroia and A-gon, in this order. Let the top quickest men of the team in base, put the one with the best contact worry the pitcher even more and as a final act, let the power hitter smash the ball out of the park.
Ellsbury is used to be the leadoff man, we put Crawford in a confortable position so that he can use his full potential, the third man, the contact man, will have an even more easy chance to contact, as the pitcher will probably be afraid of (dozens) stolen bases and the power hitter to destroy the concentration of the pitcher.