When the outcome was in the balance in the last three minutes, the Pistons desperately needed to get a stop for a chance to stay close to the surging San Antonio Spurs. The shot went up and four Pistons defenders started going the other way, almost assuming that Andre Drummond would get the rebound. It’s a reasonable expectation, as Drummond is the best rebounder in the league. If the Pistons had been able to garner the rebound, they could have gotten in transition to try to get an easy basket. Instead, the Spurs got the basket and a quick whip pass to LaMarcus Aldridge resulted in an easy lay-in. The sequence was part of a 12-2 run, after which the Spurs took their largest lead of the game and went on for a 96-93 victory on Monday night. The mentality and poor execution frustrated coach Stan Van Gundy, who has seen the Pistons’ rebounding effort and production fall sharply in the past few weeks, coinciding with their three-game skid. “We have other guys who are good rebounders. Nobody’s numbers will look good playing with Andre, because he gets so many that your numbers come down,” Van Gundy said. “A guy like Avery (Bradley) who averaged over six rebounds last year and Reggie (Jackson) — who in the past has been a big rebounder — their numbers fall.