Watching the decline of the Dallas Mavericks

The past few offseasons have not been kind to the Dallas Mavericks. This summer they lost out on DeAndre Jordan in spectacularly infuriating fashion. But since their title in 2011 they’ve also been spurned by the likes of Dwight Howard and Deron Williams, unable to turn cap room into an elite player. In that first summer after winning it all, Dallas let Tyson Chandler go as part of a plan to hopefully lure a more compelling star to pair next to Dirk. That second star has never materialized and, for the fifth year in a row, they enter a season with a collection of intriguing, albeit flawed parts, to try and build something special with.

In the first two seasons immediately following the title, the Mavericks’ win percentages dropped but they’ve bounced back with seasons of 49 and 50 wins in the last two. That’s a far cry from the 57-win season where they won the title, or the 55-win season that preceded it. But it’s something approximating competitiveness, especially in the loaded Western Conference. The interesting thing is, despite missing out on big names, the Mavericks have actually done fairly well cobbling together a workable supporting cast.

The graph below shows Dirk Nowitzki’s Box Plus-Minus[1. A box score derived estimate of a player’s net impact per 100 possessions] by season, as well as a minute-weighted average BPM for the rest of the roster.

While the quality of the Mavericks’ supporting cast did drop off fairly sharply in those first two post-title seasons, it steadily climbed over the last two. In fact, last season’s supporting cast had a minute-weighted average BPM of 0.9, which equates to roughly the quality of 43-win team without even taking Dirk into account. In fact, it was tied for the third-best supporting cast of Dirk’s career. The bigger problem with the Mavericks’ struggle to stay competitive has been Dirk’s decline.

Obviously, the big name free agents Dallas was chasing were not just about winning more title in the present, but also about creating a bridge to a competitive future as Dirk aged. Without those personnel coups, things have likely played out exactly as the Mavericks front office projected — Dirk has declined and so has the team. However, the supporting cast has likely taken an unfair share of the blame, simply by virtue of not being A-list stars. All things considered they’ve actually performed quite admirably and, according to BPM, last season was actually the first time since his rookie season that the rest of the Mavs were, collectively, better than Dirk.

None of this should inspire confidence about the upcoming season. In their season previews, FiveThirtyEight projected Dirk with an impact of just +0.4 per 100 possessions this season, about half as effective as he was last season. The rest of the team, however, is projected to be much worse — a minute weighted average of -0.5 per 100 possessions which would tie them for the worst supporting case of Dirk’s career along with the group he played with as a rookie. There are some potential wild cards on the roster but in all likelihood this is where those free agent misses will finally be felt. Dirk’s effectiveness has dwindled towards average and the rest of the roster has slipped even below that mark. The only way forward is to wait for next summer and try their luck again in the free agency lottery[2. No Whammys, No Whammys, No Whammys, No Whammys, No Whammys].