There have been 3,071 NBA players over the past 50 years. Guess how many had a better start than James Harden.

Last week I made a statement that should give anyone pause: The first four years of James Harden’s career were on par with the best players in NBA history. And I wasn’t just referring to All Stars or hall of famers. I was referring to the top 20 players of the past 50 years. It’s reasonable to wonder whether I manipulated the data or analysis in some way to make Harden look better than he actually is. I wondered the same thing myself, so I spent hours digging into the data and came to an amazing conclusion: James Harden’s first four years were better than that statement suggests.

To say that Harden’s first four years were on par with the greatest players in history isn’t necessarily impressive if a lot of other, non-superstar players had similarly good starts. 3,071 players have entered the league in the past 50 years, so even if only a small percentage of those players ended up having superstar careers, you’d still expect that hundreds of players would have at least started their career on par with the superstars. (Consider that hundreds of those 3,071 players went on to be All Stars and 61 have already been inducted into the Hall of Fame.) But when I looked at the data, here’s what I found: Of all players in the past 50 years, there are only 12-17 who started their career as well or better than James Harden. Namely, there are 12 players who played as well or better at ages 22 and 23: LeBron James, Tim Duncan, Shaquille O’Neal, Chris Paul, Dwight Howard, Dirk Nowitzki, Kevin Durant, Tracy McGrady, Andrei Kirilenko, Chris Bosh, Kevin Love, and Bob McAdoo. And there are 17 players who played as well or better in their third and fourth season: LeBron James, David Robinson, Tim Duncan, Shaquille O’Neal, Chris Paul, Michael Jordan, Kareem Abdul-Jabbar, Dwight Howard, Dwyane Wade, Dirk Nowitzki, Charles Barkley, Manu Ginobili, Larry Bird, Kevin Durant, Andrei Kirilenko, Kevin Love, and Bill Walton.

Now your brows should really be furrowed. Could it possibly be true that the start to Harden’s career was that good, this being a guy who was once the third best player on his team, who spent the first few years of his career playing behind Thabo Sefolosha? I’ll defend the finding in a minute, but first I’ll briefly explain how I arrived at it.

I have a database of all players in NBA history, which I painstakingly built using pages from Basketball Reference. I merged onto this database RAPM data (available from here), which a lot of people consider the best performance metric because, unlike most of its competitors, it includes a good measure of defense. I primarily used RAPM in my analysis, but RAPM data only go back to the 1990-91 season, so I included two other decent metrics: PER and WS/48. Both metrics are available from Basketball Reference and both have fairly convoluted calculations (you can read about WS/48’s calculation here), but essentially they aggregate traditional box score statistics into a single measure of performance. To normalize the metrics, I calculated how many standard deviations above or below average every player was for every season of their career. Then I averaged the normalized metrics, giving the most weight to RAPM. Finally, I limited the sample to players who entered the league since 1963 (so 50 years of data) and seasons in which they played at least 500 minutes, and counted how many players had a better start than Harden, and those are the results you see above.

It’s reasonable to wonder whether some fishy statistical manipulation is producing these incredible results. Here’s the only way I know how to defend its validity: Look for yourself! Browse Basketball Reference and see if you can find other players who had a better start than Harden. You might be able to find a few who came close, but not many, and certainly not many non-superstars.

Of course past performance is no guarantee of future performance, and there is cause for concern with the way Harden’s performance has slipped this season, but what these results imply is that the Rockets could very well have one of the future all-time greats on their roster. (Actually two, if you count Howard, but I’m pessimistic that he will ever return to pre-back-surgery form, as explained here and here.) It cannot be understated how significant this is for the Rockets because history has shown that unless a team has at least one of the all-time greats playing in his prime, they are extremely unlikely to win a championship or even make the Finals. Luckily for the Rockets, Harden is still young and probably won’t start playing his best ball until the next year or two.

The bottom line: Given Harden’s likely trajectory (and the Rockets’ financial flexibility, whip smart GM, and excellent center), there are few, if any, teams that are likely to have more success than the Rockets over the next 5 years.

(P.S. – I am beginning to understand why Bill Simmons was and continues to be so emotional about the Harden trade [what he calls “the Harden Disaster”]. It’s frightening to imagine what that Oklahoma City team could have been.)