The Spurs' recent success can be traced back to their improvement on defense. The addition of Kawhi Leonard, Danny Green and Tiago Splitter allowed San Antonio to regain the identity they had during previous championship runs. The old adage that defense wins championships is not exactly accurate, but being able to lock up opponents certainly goes a long way towards being a true contender.

The changes to the roster during this past offseason, while obviously positive on the aggregate, could mean a regression on the defensive end. Losing Tiago Splitter and Aron Baynes without finding a proven replacement is a risky move that puts a lot of pressure on LaMarcus Aldridge to improve as a defender.

Fortunately, he has the physical tools and basketball IQ to help the Spurs remain among the best teams in defensive efficiency. He just needs to improve on specific areas in which focus and effort go a long way.

Aldridge is a very good post defender

With Robin Lopez taking the toughest assignments, Aldridge ranking in the 88th percentile as a post defender according to Synergy Sports seems deceiving. Going through video of his matchup against Zach Randolph in the first round of the last playoffs, however, provides evidence of Aldridge's ability to use his quick hands and his length to contain post brutes.

With Aldridge as the closest defender, Z-Bo shot 36 percent from the field, according to SportsVU data. It's not a coincidence. Blake Griffin went 2-for-13 from within 10 feet. Aldridge is strong enough to not be easily overpowered and puts his 7'5" wingspan to good use to block or bother shots.

In terms of post defense, the Spurs are not downgrading significantly from Splitter, which will be important when dealing with traditional teams in the postseason.

Aldridge' struggles with stretch bigs are concerning but might be system-related

While Aldridge can hold his own when his matchup tries to get close to the hoop, he doesn't fare as well when he has to meet them in the perimeter. On the aggregate, opponents shoot two percentage points worse than usual when Aldridge is defending them, per SportsVU data. Beyond 15 feet, however, his impact is negligible. On three-pointers, opponent's shoot better when he's on them than they typically do otherwise.

Those numbers are somewhat surprising, considering Aldridge's agility. He's not a freak like Serge Ibaka or Anthony Davis but he's also far from a stiff. Aldridge can move his feet, often staying with guards on switches or after ball screens. Yet it's not unusual to see him offer little resistance on jumpshots, even to knockdown shooters.

Late contests like that one are not acceptable when guarding Nowitzki. Dirk went 7-for-14 against Aldridge, including three three-pointers. He was on average 5 feet away from Dirk on his attempts. For comparison, last season Splitter held Nowitzki to 7-for-16 shooting during their matchups with no three-pointers by defending him at an average distance of 3.3 feet.

Fortunately, Aldridge not stepping to the perimeter probably has a lot more to do with Terry Stotts' defensive philosophy than anything else. Stotts adopted conservative principles and took them to the extreme.

"We looked at Indiana and Chicago and San Antonio and they were very conservative in their approach," Stotts told The Oregonian's Mike Richman in March. "They protected the paint, they dropped on pick and rolls, they took away angles to the basket. That was the process going into last year."

While it's true that the Spurs prefer to allow mid-range jumpers than shots near the rim, they do have their power forward show on pick and rolls and on occasion put an emphasis on contesting every shot. It's a small adjustment and Aldridge has the foot speed to do it. Whether he puts in the work consistently on top of handling a big offensive burden, however, is a concern.

Protecting the rim will be a challenge

The Spurs have one elite rim protector in Tim Duncan. When he's on the court, they will be fine in that area. Who protects the rim when Big Fun is on the bench is unclear, though.

David West and Boris Diaw simply don't have the length, the hops or the instincts to do it. Boban Marjanovic is so big that he should be able to deter, change or block shots but opponents will have him come out to the perimeter whenever they can by involving him on pick and rolls. Aldridge will be relied upon to protect the rim as much as he was with the Blazers before Robin Lopez joined the team.

That's a problem because Aldridge is not a great help defender. He allowed a very good 45.1 percent on shots he contested at the rim last season but only challenged a shot every 5.8 minutes lasts season. Good rim protectors are much more active than that.

Aldridge is an excellent shot blocker when he's on the ball on post up or on pick and rolls. He's just not the type of weak side help defender that covers ground and changes shots. He's much, much better at making the second rotation than he is the first. That's one of the main reasons why he's better suited to play power forward and not center.

Once again, Aldridge should be able to improve on that area as long as he buys in. He will simply need to show a willingness to play like a center that wasn't always there in Portland.

Can the Spurs remain elite on defense?

It will be hard for San Antonio to keep the second best defense in the West with the current personnel. They managed to do just that without Splitter for most of the season but they had Baynes emerging as a solid team defender who could take up space and contest shots.

As we learned with Richard Jefferson, expecting players to completely change their game when they join the Spurs is a recipe for disappointment. There is a chance, however, that Aldridge truly dedicates himself to becoming a more versatile and consistent defender. If he does that, a top five finish in defensive efficiency is not out of the question.

The Spurs can survive the regular season without Aldridge improving on his flaws but will certainly need him to tighten up his rim protection and defense on perimeter bigs in the postseason. Whether he can do that or not could be the difference between a deep run and an early exit.