The Dallas Mavericks have a lot to work on after losing Game 1 to the Houston Rockets, none more pressing than pick-and-roll defense. One of the things that makes the Rockets so difficult to guard is that all four of their big men - Dwight Howard, Terrence Jones, Josh Smith and rookie Clint Capela - have the length and athleticism to be a threat rolling to the rim. With James Harden dominating the ball and the other perimeter players spotting up along the three-point line, Houston can isolate and attack either of the opposing big men in the pick-and-roll at any point in the game.

The Mavs brought in Tyson Chandler to fortify their defense but there isn’t much he can do when the Rockets force Dirk Nowitzki to defend in space 25+ feet from the basket. Dirk on one of the Houston big men, usually either Smith or Jones, was money in the bank for Houston whenever they wanted it. He moves so slowly that the Rockets PF’s had an ocean of space to force Chandler to commit to them and both Jones (6 assists) and Smith (1 assist) have the passing ability to throw the lob to Howard or find one of the shooters. Ball movement off penetration is why Jason Terry (4-7) and Corey Brewer (3-5) were able to light up Dallas from beyond the arc on Saturday.

One of the biggest differences between the regular season and the playoffs is the other team has time to dig into the scouting report and tailor fit their game plan to attack any weakness. The playoffs are the NBA’s brightest stage - every hole in a player’s game will be exposed. Dirk’s defense has never been stellar but his lack of lateral quickness and overall energy on that side of the ball has been an ever growing problem. The craziest part about these numbers is they don’t even factor in all the juggling Rick Carlisle does to keep Dirk out of the worst types of matchups on defense:

At this stage in his career, there’s just nowhere you can hide Dirk on defense against a good team, especially one with an offense as potent as the Rockets. Even if you slide him over to the SF position, which is something I talked about in my preview of the series, he still has to chase either Trevor Ariza or Corey Brewer around screens and find them in transition on cross-matches. Maybe the biggest overall concern is the Mavs give up a lot of open 3’s with Dirk on the floor and no team in the NBA shoots more 3’s than Houston.

Playing defense in the modern NBA is all about stopping the two-man game and there might not be a PF or a C in the league with a worse chance of doing that than Dirk. It makes sense when you consider how old he is, especially in comparison to the other starting PF’s on Western Conference playoff teams.

1. Draymond Green - 25

2. Terrence Jones - 23

3. Blake Griffin - 26

4. LaMarcus Aldridge - 29

5. Zach Randolph - 33

6. Tiago Splitter - 30

7. Dirk Nowitzki - 36

8. Anthony Davis - 22

PF has become a young man’s game. It’s not just about holding your own in the post, cleaning the defensive glass and protecting the rim - none of which Dirk does very well either - you also have to be able to slide your feet in a stance and cover ground out to the three-point line. The way the league is going, it’s all about pace and space and that starts at PF.

There’s a reason most of Dirk’s peers -- Tim Duncan, Kevin Garnett, Pau Gasol -- have slid down to C as they have gotten older. It’s harder to expose lack of footspeed in the paint and it’s easier to design a defense that minimizes the need for your big man to extend too far out on the perimeter if he is tasked with protecting the rim. The problem for Dirk is he could never play interior defense well enough to be a C, which forces Carlisle into a real tight bind when it comes to setting his line-ups.

Given where Dirk is physically, you want a minimum of two elite athletes next to him at C and SF to compensate. That’s what the Mavs did in 2011 when they had Chandler and Shawn Marion cleaning the defensive glass and guarding all types of frontcourt players. Four years later, Chandler is older and not as mobile while Chandler Parsons isn’t nearly the caliber of defender as The Matrix. The guy who would help the most is Al-Farouq Aminu, but inserting him into the line-up causes a numbers crunch at the other positions.

Dallas still needs Chandler to anchor the defense and Parsons to spread the floor, so having Aminu and Dirk on the floor together means taking one of the Mavs guards out of the line-up. They don’t trust Monta Ellis to run point, Devin Harris to stay healthy or Rajon Rondo to shoot, so there’s no easy answer as to which guard to leave out there with a jumbo-sized line-up. The most radical notion and the one Carlisle likely isn’t going to try until his back is against the wall is benching Dirk.

While that may seem drastic given how well he can still play on offense, there may not be another solution if the Mavs want to slow down the Rockets offense, which scored 118 points on Saturday even with Dwight Howard in foul trouble for most of the game. Dirk may be the face of the franchise but there’s a reason he’s only making $8 million a season - he’s a more limited player than in his prime. A team that starts Dirk at one of their frontcourt positions has little chance of surviving the Western Conference gauntlet and might be capped out as a first-round loser.

No matter how you spun the matchups, Dallas was probably in trouble. Dirk would have had no answer on the glass for Zach Randolph and Marc Gasol in a series against the Grizzlies and he would have been eaten up in the two-man game by Blake Griffin and DeAndre Jordan in a series against the Clippers. For as great a coach as Carlisle is, there’s only so much he can do when he has to ask a 36-year old to play defense against the best players in the world. He might try to go more zone as the series goes on, but it’s hard to see gimmick defenses holding up against a team that spreads the floor and passes the ball as well as the Rockets. He did the best he could to junk it up against the Spurs last season and that ended with a 23-point loss in Game 7.

In the four seasons since the Mavs won the championship, they have finished as the 8 seed, the 10 seed, the 8 seed and the 7 seed. Just about every spot on the roster has turned over except Dirk and they don’t appear all that much closer to advancing in the playoffs than they were in 2012. It’s a tough pill to swallow for Dallas fans who have watched Dirk excel at the highest levels of the game for well over 15+ years, but as Charles Barkley always says, Father Time is undefeated.