The Celtics understood they needed to do a better job on the boards as the series shifted to New York, and they made good on their word. According to Basketball-Reference, the Celtics' defensive rebound rate in Game 1 was just 69 percent, and in Game 2, it was a miserable 58.3. But in Games 3 and 4, the Celtics rebounded, literally and figuratively. They posted a defensive rebound rate of 71 in Game 3 and a more impressive 77.2 in Game 4. (Accordingly, the Knicks' offensive rebound rate was significantly lower in both games compared to the opening two games in Boston, ultimately bottoming out at 22.8 in Game 4, although they did still manage to score 18 second-chance points).
The Celtics will have to keep that momentum going against the Heat, who are a better rebounding team than the Knicks. The last thing you want to do is give LeBron and Wade extra looks at the basket.
Bonus links (aka your requisite Jackie MacMullan and Bob Ryan reading assignments)