Complex sentence: In a game against the New York Yankees during the regular season, Castillo dropped a pop-up hit by Alex Rodriguez, which allowed both the tying and winning runs to score, giving the Yankees a 9-8 win.
Split into simpler sentences: In a game against the New York Yankees during the regular season, Castillo experienced problems catching a pop-up fly ball. The ball, hit by Alex Rodriguez, was dropped by Castillo, which allowed both the tying and winning runs to score, thus giving the Yankees a 9-8 win.