Milton Aguilar (born 2 March 1984, in Mexico City) is a goalkeeper for Alacranes de Durango. He used to be the third goalkeeper at Club América, after Guillermo Ochoa and Armando Navarrete. Milton used to play for the Primera A (2nd Division) team of Club América, Socio Aguila
Milton Aguilar is not a first string player.
The story says that Milton Aguilar was a third goalkeeper and that doesn't sound like he's a first string player, but you never know. He might or might not be. I don't think the system knows what first string means in this context. 
( z1 person :ARG0-of ( z2 play :polarity - :mod ( z3 string :ord ( z4 ordinal-entity :value 1 ) ) ) :domain ( z5 person :name ( z6 name :op "Milton" :op "Aguilar" ) ) )