Last week I addressed the benefits that Dwight Howard would bring on offense; this week’s column looks at how Dwight will help on the other end of the floor. The Rockets were a middle of the road defensive team last season. With the addition of a (hopefully healthy) Howard, there is every reason to believe that the Rockets can fashion a top-10 defense and become legitimate championship contenders next season.Last season’s Houston Rockets gave up 103.5 points per 100 possessions, a defensive rating that was tied with the Knicks for 16th in the NBA. A number of issues stand out when scrutinizing specific defensive data: despite having a quality rim-protector in Omer Asik, the Rockets gave up a 63% FG% in the restricted area, the 6th highest in the league. Houston also gave up the 2nd highest percentage on corner three’s (43.4%) and the 9th highest percentage on all three-point shots (37%) while allowing opponents to take the 4th highest number of three’s per game (22.4). In short, Houston, a team that values taking efficient shots on offense, did not do a particularly good job of taking away such shots on defense.Omer Asik was undoubtedly the defensive anchor of last year’s Rockets team. Houston was 5.5 points per 100 possessions better with Asik on the floor than off. In other words, in the 18 minutes per game in which Asik didn’t play, Houston’s defense transformed from the equivalent of the Bulls’ 5th rated defense to that of the Piston’s bottom-10 unit. With Asik on the court, Houston’s opponents took more mid-range shots and fewer three-pointers. Of the four most oft-used Rockets line-ups (all of which featured Asik), three rated better than league-average defensively. All four line-ups had four players in common: Jeremy Lin, James Harden, Chandler Parsons, and Asik; the fifth player varied among Patrick Patterson (the worst line-up defensively, allowing 106.0 points per 100 possessions), Marcus Morris (the best line-up defensively, allowing 95.8 points per 100 possessions), Donatas Montiejunas, and Carlos Delfino. While three of these line-ups include players who are no-longer with the Rockets, the take-away is clear: with Asik in the game, the Rockets were an above-average defensive team.Dwight Howard has had a similarly pronounced defensive impact on his former teams. The Lakers, ranked just behind the Rockets in defense last season, were a top-3 defense with Howard on the court and a bottom-10 unit with Howard on the bench. In Orlando, the Magic were also significantly better on defense with Howard on the court. In particular, Howard’s Magic teams excelled at defending the restricted area and the three-point line, two areas in which the Rockets’ defense struggled last season. In the ’08-’09 season, Orlando allowed the 3rd fewest corner three attempts; in ’09-’10 the Magic allowed the 5th fewest such attempts. In ’08-’09, Orlando was the 2nd stingiest team in the restricted area (allowing a 56% FG%) and in ’09-’10 they were again the 2nd stingiest team at 57%.Despite often playing with so-so defensive teammates, Howard’s Orlando teams consistently ranked among the best in the league. Indeed, the Magic ranked in the top 3 in defense for three consecutive years from 2008 until 2011. The most oft-used line-ups on these teams were not exactly teeming with defensive aces outside of Dwight. In the ’08-’09 season, line-ups featuring Howard, Rashard Lewis, Hedo Turkoglu, Jameer Nelson and one of Keith Bogans/Courtney Lee/Mikael Pietrus defended at an elite level. In ’09-’10, the Howard-Matt Barnes-Vince Carter-Rashard Lewis-Jameer Nelson line-up logged a whopping 772 minutes and held opposing teams to a paltry 95 points per 100 possessions. In ’10-’11, the Howard-Brandon Bass-Jameer Nelson-Jason Richardson-Hedo Turkoglu line-up logged 630 minutes and only gave up 94.4 points per 100 possessions.The upshot is that a healthy Dwight near his defensive peak can almost single-handedly ensure a top-10 defense. Outside of Asik, the Rockets’ starters from last season are not markedly better or worse defensively than the players that Dwight played with on Orlando. Next season, the Rockets will have the opportunity to have a top 6 or 7 defensive center on the court on all times. That fact alone should improve the Rockets defensively and propel Houston to within spitting distance of the elite-tier of NBA defenses.