Whenever the topic of rookie of the year comes up, the first thing people who argue for Ben Simmons will bring up is that Simmons is fifth in the league in assists at 8 per game, while Donovan Mitchell only averages 3.6 per game. Thus, Simmons is clearly a better passer and delivers more value to his team than Mitchell. But what these people are missing is why assists are valuable in the first place. As I will show, looking at things from that perspective show that Mitchell is a far superior passer.

Assists are valuable because an assisted shot is better than an unassisted one. Otherwise every team would just go iso on every possession. So just looking at raw assists totals is about as useful as looking at raw scoring numbers- sort of informative, but needing efficiency numbers. For example, if on one possession, Donovan dribbles down the court, sucks in the defense, and finds a wide-open Joe Ingles in the corner, then Mitchell has created a lot of value on that play. But if on the next play he struggles in iso for 20 seconds and dumps it off the Gobert for a contested midrange jumper, then he hasn’t created the same amount of value, and in fact that value is most certainly negative. But if both shots go in, they are both counted as 1 assist. That’s why I analyzed and developed some of my own stats to further illuminate why Mitchell is a very good passer and Simmons is a below average one, despite the latter averaging more than twice as many assists.

Two already developed stats that you’ll need to be familiar with are potential assists and adjusted assists. Potential assists are to assists and FGA are to FGM. If you pass to someone and they miss, it’s still a potential assist. Adjusted assists are to assists as Effective Field Goal % is to field goal %. An assist on a 3 pointer counts as 1.5 assists. Strangely enough, I couldn’t find any stat for Adjusted assists/potential assists, so I downloaded some data from nba.com and made my own, assisted EFG. It’s the effective field goal percentage on shots a player assists on, and it provides a better view into the value that player creates with his passing. So, back to the ROTY debate. What’s Simmons’ assisted EFG? A paltry 56.3%, good for 88th among the top 100 players in potential assists per game. The only players below him not on lottery teams are James Johnson, CJ McCollum, and George Hill, who spent the majority of his season on the kings. Conversely, Donovan Mitchell has an assisted EFG of 63.3%, good for 24th among the top 100 in potential assists per game. League average EFG% is 52.1%. So while Simmons averages a lot more assists, Donovan’s are a lot more valuable. Simmons creates good shots, Mitchell creates great ones.

But perhaps this analysis is unfair to Simmons. One of the hallmarks of advanced stats in basketball is the tradeoff between efficiency and volume. Presumably as a player’s potential assists per game goes up, their assisted EFG goes down. So I created two more stats to get around this problem. The first is simple points added, which is calculated as such: SPA=(Assisted EFG-League average EFG)*Potential assists*2. This essentially takes the value of a potential assist as the differential between its EFG and league average EFG, then multiplies that by the number of potential assists per game. It then multiplies by 2 to get points. This gets past the volume/efficiency problem. Creating a whole bunch of league average shots doesn’t improve your SPA, so a player who creates 4 great shots and 6 exactly average ones is rated the same as if he only created the first 4. It also then properly rewards players with a higher volume of potential assists. It was simple enough to make, but I had some problems with it. Namely, it rewards being on a good team and punishes being on a bad team. It stands to reason that creating a 53% EFG shot for the kings is valuable, but the warriors should expect to do better than that on a given possession. So I created Adjusted Points Added, which is the same as Simple Points Added, but it replaces league average EFG with team EFG, which provides a better proxy for what the replacement level shot is. It was a pain to create, requiring an IF= function with 30 arguments, but worth it in the end. The results were a little bit surprising, but not too much so. They should probably also tip the ROTY race in Mitchell’s favor.

Ben Simmons ranks 56th in Adjusted Points Added, with 72 on the year. This is largely because while he gets a lot of assists, the difference between his assisted EFG and his teams EFG is only 3%, 56.2% to 53.2%. Donovan Mitchell, on the other hand, ranks 2 spots ahead of LeBron James with 106 Adjusted Points Added, almost 50% more than Simmons. This is mostly because while on a smaller volume, Mitchell’s differential between assisted EFG and Team EFG is 9.5%, at 63.2% to 52.7%. So APA rates each Mitchell assist as more than three times as valuable as each assists from Simmons. Most people think the ROTY race is pretty close right now, and would also argue the biggest point in Simmons’ favor is assists. But if that’s a measure squarely in Mitchell’s favor, then the contest really isn’t much of one. Simmons’s case essentially boils down to a 6’10" guy outrebounding a 6’3" guy.

I mostly made this for ROTY debate purposes, but there’s some other interesting insights I’d like to add, in no particular order

Lou Williams is more than just a scorer. The clips shoot an insane 74% EFG off his passes.

Joe Ingles is a top 5 small forward.

Jeff Teague is actually a pretty good offensive point guard, even if he is terrible person

JJ Barea might actually be good against other teams too

Bradley Beal can be a point guard. CJ McCollum Can’t.

If you call Lebron James Cleveland’s point guard, and Nikola Jokic Denver’s, then the only starting point guard with a worse APA than Simmons in Memphis’s Andrew Harrison. Then again, Tyreke Evans and Marc Gasol still rank above Simmons and Mike Conley’s been hurt all year. Shelvin Mack ranks 49th for Orlando, and Jameer Nelson 50th for Detroit. So yeah Simmons is hardly great passer. His Teammate Embiid actually ranks higher than him on this list by two spots.

Anyways, I hope you guys enjoyed this and I apologize for any formatting errors, this was my first fanpost. I couldn’t figure out how to get text below a chart here at the bottom is the top 100 players by potential assists per game ranked by Adjusted Points Added. You may have to scroll over at the bottom to see the final column, which is kinda the whole point of this analysis. I apologize for that.