For Heat, it's now all about D

Dwyane Wade and LeBron James have showcased their lockdown skills at the end of games. Gregory Shamus/Getty Images

When the Miami Heat signed LeBron James to play alongside Dwyane Wade, speculation centered on what two of the league's best scorers could do playing together. As it turned out, more attention should have been paid to the other end of the court.

In the regular season, Miami was the league's most balanced elite team, ranking third in the NBA in offensive rating and fifth in defensive rating. The Heat's run to the NBA Finals, however, has been powered more by defense than by its offense. Miami has allowed just 101.8 points per 100 possessions, best of any team that advanced past the first round.

The success of the Heat's defense could be diminished because Miami did not match up against an elite offense in the first round. The 11th-ranked Chicago Bulls were the best of the three offenses the Heat beat on the way to winning the Eastern Conference. The Dallas Mavericks, who boast the NBA's best offense in the playoffs by a wide margin, represent a significantly greater challenge in the NBA Finals. Miami met it in Tuesday's series opener, holding the Mavericks to barely more than a point per possession -- Dallas' second-worst offensive performance of the playoffs.

Overall, the Heat have held playoff opponents 7.2 percent below their regular-season efficiency. That puts Miami in elite territory. Only the Boston Celtics (8.3 percent) have been better. The Heat have surpassed the vaunted Bulls (6.6 percent), earning praise from ABC's Jeff Van Gundy as the league's best defense. So, what is it that makes Miami so effective? Here are four things: