Complex sentence: In many minds the use of replacement players invalidated the season that was, especially in New York, where the SuperBowl XXI Champion Giants went 0-3 with replacement players, and missed the chance to defend their title.
Split into simpler sentences: In many minds the use of replacement players invalidated the season that was. The semtiment was especially felt in New York, where the SuperBowl XXI Champion Giants went 0-3 with replacement players, and missed the chance to defend their title.