A few weeks ago the Dallas Mavericks traded for Jason Kidd. At the time, this move seemed somewhat desperate. Yes, Kidd is one of the most productive players in the game. But at 35 years of age, he seems to be closing in on the end of his career (although his production suggests otherwise).
At the time the move was made it was clear the Mavericks had to do something. Last year – led by MVP Dirk Nowitzki – the Mavericks boasted a 7.8 efficiency differential (offensive efficiency minus defensive efficiency). No, this wasn’t the best mark in the league (the Spurs had a mark of 9.1). Still, Dallas was clearly a title contender in 2007 (despite the actual playoff results).
When this trade was made, though, the Mavericks differential was only 4.3. Six teams bested this mark in 2006-07. So it didn’t look like Dallas was going to contend for a title this year (see The Missing MVP for an explanation of why this team had faltered).
To make the trade work, though, the Mavericks had to give up Devin Harris and DeSagana Diop. Harris and Diop are not quite as productive as Kidd. Still, both are above average and hence the benefit of adding Kidd was reduced.
In fact, when we look at the team’s record, it looked like the subtractions actually exceeded the addition. The Mavericks efficiency differential when this trade was made was consistent with a team that would win 52 games in a full season. Such a team could expect to win about 11 out of each 17 games played. But in the 17 games the Mavericks played with Kidd on board (and yes, that is a small sample), the team only won 10 contests. And all seven losses were to teams with winning records.
Of course, wins and losses are not the only way we evaluate teams. When we turn to efficiency differential, we see the Mavericks posted a mark of 7.4 in the first 17 games after Kidd was acquired. This mark is consistent with a team that would win 60 games in a full season, or 12.4 of each 17 games played. In sum, it looks like Kidd – who is just about as productive with the Mavericks as he was with the Nets (Win Score per 48 minutes was 12.7 in both places) — actually did help Dallas.
Unfortunately, after 17 games the Mavericks lost Nowitzki. With Kidd, Nowitzki had raised his WP48 (Wins Produced per 48 minutes) from 0.218 to 0.319 (similar to the 0.306 mark he posted last year). Without Nowitzki, though, the Mavericks now have to turn to Malik Allen (WP48 of 0.026), Juwan Howard (WP48 of -0.113), and Brandon Bass (WP48 of 0.055).
Bass is the best of the bunch, and he is still below average. If the Mavericks were to replace Nowitzki with Bass for an entire season, the team would lose about 16 more games. In other words, the 60 win title contender would morph into a 44 win also-ran. Fortunately, Nowitzki is not lost for the entire season, just a few weeks. Nevertheless, in a very competitive Western Conference, the loss of Nowitzki might be enough to drop Dallas out of the playoffs completely.
And if that happens, I suspect people might think the Kidd trade was clearly a mistake. I think, though, that the numbers tell us – both before and after the fact – that this move was a good idea. Unfortunately, a bit of bad luck here and there, certainly makes the story appear quite different.
Our research on the NBA was summarized HERE.
Wins Produced, Win Score, and PAWSmin are also discussed in the following posts:
Finally, A Guide to Evaluating Models contains useful hints on how to interpret and evaluate statistical models.