The San Antonio Spurs have a big problem without Tim Duncan

Tim Duncan can spend as many long nights as he wants in the San Antonio Spurs practice facility. He can continue his 20-year tradition of being the last one out of the gym until the building crumbles around him, lost to the ravages of time. Unless the Hall of Fame big man decides to come out of retirement and fix the Spurs defense, San Antonio can wave goodbye to any title hopes this season.

It is no great revelation to say that the Spurs miss Duncan, to be sure, but a 101-99 loss to the Houston Rockets on Wednesday crystallized just how much has changed for the Spurs in one offseason. Even in the twilight of Duncan's career, he kept San Antonio airtight on defense. Last season, the Spurs finished No. 1 in defensive rating, allowing less than a point per possession.

This season, the Spurs are trying to replace the Big Fundamental with the likes of LaMarcus Aldridge, Pau Gasol and David Lee — all good players in their own ways, but none of them could stop a runny nose. Suffice it to say that the results have been less than inspiring.

San Antonio entered Wednesday's game against the Houston Rockets ranked 11th in the league in defense. Although it's early, that one statistic alone should scare Spurs fans. Since Duncan's rookie year, San Antonio has fallen outside of the top 10 in defense just once: the 2010-11 season (via Basketball-Reference). As Spurs faithful will remind you with more than a hint of exasperation, Gregg Popovich's team suffered an astonishing first-round playoff exit to the Memphis Grizzlies that year, leading to a renewed commitment to outstanding execution on both ends of the floor.

While it's too soon to panic, the Spurs are already in need of that same soul-searching this year.

Call it an overreaction if you want. San Antonio undoubtedly had its hands full against the Rockets. Perhaps one might go so far as to excuse defensive shortcomings against Mike D'Antoni's squad, now that the maestro behind the “Seven Seconds or Less” Suns has another savant leading his basketball symphony. James Harden has evolved into an all-around offensive dynamo — equally adept getting to the line, finishing at the rim or finding teammates for wide-open looks. With him making his case as the NBA's MVP on a nightly basis; even the association's best defense will struggle to contain him this season.

In the end, the Spurs' 101-99 loss came down to the final possession, with neither Kawhi Leonard nor Aldridge able to buy a game-tying bucket. If San Antonio knocked down an open look or two, they would have escaped with a win. So this is much ado about nothing, right?

Hardly. Despite the near victory, the Spurs must be concerned with every facet of their defense. San Antonio gave up far too many easy looks in transition against the Rockets, something Popovich was quick to point out in his televised in-game interview after the third quarter. Indeed, against good offenses in the early part of this season, the Spurs have surrendered a veritable parade of fast-break opportunities.

Some of that is effort (an overused cop-out for explaining defensive failures), but the larger problem is miscommunication. Simple defensive breakdowns creep into every facet of the game for San Antonio, from transition to the halfcourt game, and the biggest culprits are the Spurs big men.

Aldridge in particular needs a “Come to Jesus” moment on that end of the court. Last year, the combination of Duncan and Leonard masked most of Aldridge's deficiencies and freelancing. In 2016-17, not even Kawhi can save the Spurs from Aldridge's worst habits.

One sequence in the fourth quarter cast a harsh light on the big man's woes. With just under 10 minutes to play, the Spurs managed to storm back to take a one-possession lead. After a Houston timeout, the Rockets came out and ran a simple pick-and-roll with a secondary action on the weak side. Aldridge reacted as if aliens had landed in the middle of the AT&T Center and demanded that he recite the Constitution backward. In his confusion, he ended up on Harden.

Now, it's true the Spurs have been aggressive in their switches on defense this season. In general, that's the en vogue way to deal with the pick-and-roll. I'm willing to wager, however, that the plan wasn't for Aldridge to have to face Harden dribbling downhill with a full head of steam — especially since his Spurs teammates seem equally flummoxed by the result. San Antonio lost containment on the roller, and the Rockets got an easy look at the rim that ended in two free throws after a desperation foul.

Just a few possessions later, Harden once again forced Aldridge into a switch. You could see the joy in The Beard's eye as he flew right past the Spurs big man, finding Clint Capela for an alley-oop. The Spurs fought back, but they couldn't quite come up with stops when they needed them the most.

Short of a major change, that will be the story of this season for San Antonio. Aldridge can be an acceptable defender, but the Spurs must find a scheme that brings out the best in him. That, in turn, might put too much pressure on the perimeter defense, compromising the entire system. And unfortunately, Aldrige is only part of the problem. Gasol is even worse; Lee does his damnedest, but effort only gets you so far.

There's time still, certainly. The Spurs are dealing with a few injuries that have kept the starting lineup from playing together to start the season, and that hasn't helped; familiarity will help as the season goes on. Dewayne Dedmon is a solid, young, modern big man who will help as the year goes on. One assumes no one within the organization is anywhere close to panicking, as that's simply not the San Antonio way. By the All-Star break, there's every chance all this nonsense will be behind us.

Still, there's a dark cloud on the horizon for one of the game's preeminent franchises. In the modern NBA, the primary function of the big man is to protect the rim, yet the Spurs managed to build a roster without a plus-defender to be found in the middle. Actually, that's being generous; the Spurs don't have an average defender among their bigs. So long as that's the case, Kawhi Leonard can flirt with 40 points and stake his claim as the game's best two-way player as much as he wants. San Antonio will be left grasping at straws, trying to figure out how to compete for a championship in the post-Tim Duncan era.