Some nights, it can take a novel to properly parse and analyze all that had happened over the 48 minutes of an NBA game. This was not one of them. After the Spurs survived another lackluster performance to finally put away a pesky Cleveland team 119-113 at the AT&T Center on Saturday night, coach Gregg Popovich provided the Cliff’s Notes synopsis in five words. “Tim Duncan saved our ass,” Popovich said. Consider it the perfect headline for the 140-characters-or-less age, as brief as it was accurate. Duncan piled up 30 points, 12 rebounds, four assists and five blocks to lift the Spurs past the Cavaliers. The Spurs needed nearly every bit of it to hold off a 22-44 Cleveland squad playing without leading scorer Kyrie Irving. Duncan’s fourth block, on Tristan Thompson with 54.9 seconds to go and the Cavs within four, all but iced the game. “He obviously carried the whole night for us,” Popovich said of his 36-year-old captain. “But it shouldn’t have to be that way.” Indeed, a game after playing Dallas down to the wire in a 92-91 win — after which Popovich described his team as “playing in mud” — the Spurs offered much of the same Saturday. This time, they concentrated their struggles on the defensive end, where they allowed a Cavs team that came in averaging 97.4 points to blow past that number early in the fourth quarter.