The San Antonio Spurs are not a good defensive team.

They only have one player, the 35-year-old Tim Duncan, who averages over a block a game. Duncan was once a perennial All-Defensive team selection, but there’s very little spring left in the legs and knees of a 15-year veteran who has played in over 1,200 regular season and playoff games.

He’s not playing above the rim anymore, posting the lowest block rate of his career. But while Duncan's defensive statistics have been declining since San Antonio’s 2007 championship, the Spurs have tried to pair him with more offensive-minded big men: 6’7 DeJuan Blair and 6’10 shooting specialist Matt Bonner.

Over the years, Gregg Popovich has been widely praised as a defensive mastermind. But talent makes the scheme work in the NBA, not the reverse. There are a lot of coaches who could have designed a great defense around a prime Tim Duncan; there isn’t a coach in the NBA who could design a great defense around San Antonio’s current personnel.  

There’s a reason the Spurs have the league’s 17th rated defense: it’s open season at the rim in San Antonio. LeBron James scored 33 points on 12-for-21 shooting against them; Blake Griffin dropped 28 on 11-for-19 shooting. There’s no way to play great defense if you can’t consistently prevent people from dunking on you.

Oddly enough, the Spurs have taken on the identity of their old Southwest Division rival, the Dallas Mavericks of the early 2000’s, another offensive-minded team who couldn’t translate its regular season success to the playoffs.

San Antonio hasn’t won a second-round playoff game since 2008: in 2009, they lost 4-1 in the first round to the Mavericks. In 2010, they were unceremoniously swept out of the second round by the Phoenix Suns. Last year, despite having the league’s best regular season record, they were bull-dozed in the paint by the duo of Marc Gasol and Zach Randolph in a first-round upset.

There’s little reason to expect the team as currently constructed, even when Manu Ginobili returns from a hand injury, to be much of a threat in the playoffs this year.

After this season, their payroll drops to $47 million, as Duncan becomes a free agent. It drops to $27 million in 2013 when Ginobili’s contract expires.

If San Antonio isn’t going to upgrade around this team, there’s no reason to bring it back. But if the Spurs aren’t willing to cut ties with franchise icons like Duncan and Ginobili, they need to acquire an athletic shot-blocker who can protect the interior of the lane.

They have the pieces to make a move, as they’ve always been able to draft well, although it’s no longer as easy to hit home runs on international players like Ginobili and Tony Parker. There are too many scouts and the basketball community is too inter-connected, especially on the international level, for elite players to slip under the radar for too long.

However, some combination of Kawhi Leonard, an athletic and skilled 6’7, 225 small forward with a 7’3 wingspan, James Anderson, a skilled 6’6, 195 shooting guard with an excellent jumper and Gary Neal, an athletic 6’4, 210 combo guard, would be able to bring back something on the trade market. Good young players on inexpensive rookie contracts are worth their weight in gold in the NBA’s new CBA.

One name immediately comes to mind: Tyrus Thomas of the Charlotte Bobcats. Thomas, a 6’9, 215 forward with a 7’3 wingspan and a near 40’ max vertical, has a career block rate of 5.3 and the skill level not to harm San Antonio’s floor spacing offensively.

The Spurs are at the same turning point they were in 1997, when they had a team built around David Robinson, Sean Elliot and Avery Johnson that couldn’t take the next step. Which brings us to the other direction San Antonio could go in.

Ginobili is already missing a significant portion of the season and it wouldn’t take much to shut Duncan down the rest of the year. Flip Tony Parker for a few first round picks then amnesty Richard Jefferson and San Antonio is one of the youngest teams in the NBA, setting themselves up for a sudden plunge down the Western Conference standings for the first time since 1997.

As it happens, 2012 is another excellent year to have a bad team. The University of Connecticut has a 6’11 270 18-year old center capable of catching the ball in mid-air, taking it between his legs and dunking it violently in one motion.

Andre Drummond may be the best big man prospect since Tim Duncan; more athletic than Yao Ming, more skilled than Dwight Howard and less injury prone than Greg Oden. If that sounds outlandish, look at Duncan’s statistics as a Wake Forest freshman and imagine what Drummond would do as a college senior. He could add five years to Duncan’s career in the same way that Duncan did for Robinson, while the Spurs veteran locker room would be the perfect place for him to learn the game, especially in comparison to chaotic situations like Washington or Sacramento.

San Antonio has the roster flexibility to either get better or get worse in a real hurry. The only thing they can’t afford to do is stay in place.