Photo: Nathaniel S. Butler/NBAE/Getty Images On Sunday night, something unprecedented happened at Madison Square Garden: A legitimately exciting preseason NBA game took place. The basketball part of the evening was not itself compelling, and how could it have been? It was an exhibition, on a Sunday night, featuring mostly New York Knicks backups. It was competing for eyeballs against a Giants-Bengals matchup at the Meadowlands and Game 1 of the Mets-Dodgers NLCS . And yet. The Knicks were