Complex sentence: The New York Mets selected Haniger in the 31st round of the 2009 Major League Baseball (MLB) Draft, but Haniger did not sign with the Mets, choosing instead to enroll at Cal Poly, to play for the Cal Poly Mustangs baseball team.
Split into simpler sentences: The New York Mets selected Haniger in the 31st round of the 2009 Major League Baseball (MLB) Draft, but Haniger did not sign with the Mets. Instead, he enrolled at Cal Poly, to play for the Cal Poly Mustangs baseball team.