2013 WNBA Draft: Who's the best center prospect after Brittney Griner?

Part of the reason I like keeping track of draft prospect statistics, both before and after they've played a year in the league, is because it helps to really put in perspective just how good WNBA stars were in college.

They're not only the elite or All-American caliber players but the most efficient and productive players in the nation.

And that helps to put both the hype and reality of Brittney Griner into perspective. But it also helps to demonstrate just how strong this year's group of centers could be: there are three centers not named Griner who also appear on first round mock drafts and the stats suggest that at least two of those "other" centers could end up being better than any of those drafted last year. Digging back further - and taking Liz Cambage's two year absence from the league after her rookie season into account - this year's group has a chance to become the best overall in a number of years in terms of the number of players that actually make a roster.

What makes a star center?

For the sake of this analysis, we're defining centers or "pure interior" players as those who are not only very interior oriented but also those who are better suited to defend fives closer to the basket than chasing WNBA fours away from the basket. No matter what your take on discussions of "positionality", the lines there are indeed blurry in women's basketball: skills are more evenly distributed across positions so it's not uncommon to have centers step out and knock down threes or handle the ball. But players who can occupy the paint either to post up on offense or change shots on defense are still valuable players on a basketball court.

There isn't an easy way to tell the difference between a "power forward" and "center" statistically, so I'm relying heavily on a) the designation on their school's website and b) my take based on having watched them play. And I wouldn't blame you if you looked at some of the players we listed as a "power forwards" and wanted to put them in this group. But once we classify someone as a center, it's not nearly as hard to figure out what factors indicate a successful career in the WNBA. Those are described at length here, but the following is a quick rundown:

• Scoring efficiency: This is a pretty big one, and really the make or break one: centers with true shooting percentages under 55% usually fail to make the league whereas centers with true shooting percentages of 60% or better usually find a way to make a roster. That makes the 55-60% range a gray area, but those thresholds have held pretty steady over the last few drafts in terms of determining who will and won't make a roster.
  
• Value added: The exception to these scoring efficiency "rules" has been a value added number, which is essentially the weighted value of a player's contributions other than scoring. Having a value added rating of 2.22+ has been a "protective" factor for players. A negative value added rating - meaning a player's primary value is as a scorer - has been a sure sign of not making the league.
• Free throw rate/production: Free throw rates are another pretty clear one, though not quite the make or break threshold of overall scoring efficiency - having a high free throw rate doesn't guarantee success as much as having a low one ends up dooming many players. Either having a free throw rate (FTA/FGA) under 40%+ or a free throw production rate (FTM/FGA) under 26% have been bad signs for centers in the past.
  
• Personal foul efficiency: This is one of the few that I've found applies to all post players and I have a theory as to why that is, but having personal foul efficiency - (stl+blk)/pf - under 1.05 has been a bad sign for power forwards and centers. Those that do make rosters don't stick around long.
• Pure point rating: Although this was a metric designed for point guards by John Hollinger, he noted its application to NBA post prospects and it applies to WNBA post prospects as well. A PPR under -6.00 and a turnover ratio over 15% (meaning a center who neither creates many assists nor controls the ball well) has been a negative indicator for centers in the past (more on PPR from our early season red flags post).
  

I put those in a sort of general order of importance, but there are two things to note here: 1) scoring efficiency matters more than almost anything (so if you're wondering why your favorite center is either not on this list or ranked low, start there) and 2) offensive rebounding might not be quite as important for centers as the numbers have been all over the board in recent years.

The latter point is not only especially relevant to this year's draft but will probably be reinforced by its top pick.

The numbers

Brittney Griner

As you can tell, Griner meets just about every statistical threshold you could ask for and absolutely destroys a couple of them, but she's also not without some potential weaknesses.

The reason I used free throw production and not free throw rate is that Griner actually has a free throw rate (37.8%) beneath the threshold for a successful prospect. Interestingly, she's the only player on this list who meets one free throw criteria and not the other. The reason for that is probably two-fold: she shoots a lot of jumpers yet when she does get to the line she makes her free throws.

The other statistical questionmark about her is her relatively low offensive rebounding percentage and strength is probably a part of that: she hasn't been a player that pushes people around or gets off the ground quickly to crash the boards. But as alluded previously, that might say more about what offensive rebounding means for centers than anything else.

Kayla Alexander

While Griner's profile is definitely the strongest, Alexander's might be the most well-rounded - she doesn't really have any major weakness.

The one question mark might be about her scoring efficiency, which falls into that gray area, but that value added rating - meaning she does more than simply score - boosts her value as a prospect. As you can guess from the numbers above, a lot of that is due to that really strong offensive rebounding percentage - she's among the best in the draft in that category - but she also has the 14th best block percentage in the nation (7.6%), which is fourth among seniors and arguably the second best of anyone people consider a draft prospect.

But there's another sort of odd question about Alexander that is reflected in a surprisingly low pure point rating despite having one of the lowest turnover ratios of anyone in the draft. To come up with these player similarity ratings, I use a percentile ranking function - it takes the numbers for all 345 players over the last five years that I've put in a spreadsheet and assigns them a percentile for their scoring, perimeter, and interior tendencies. So for example, the player with the highest scoring tendencies would get a 100 while the lowest would get a 0. Alexander got a 0 for her perimeter tendencies due to the combination of a low steal percentage (1.2%) and an extremely low assist ratio (1.84%).

So does it matter that Alexander has the lowest perimeter tendencies of any prospect (drafted and some undrafted) since 2008? I honestly don't know the answer to that. Normally a low pure point rating might reflect a center who struggles to pass out of double teams, but she has such a low turnover ratio that it's hard to even put that label on her. Then there's the question of whether she was kicking the ball out from the post and people just weren't knocking down shots or driving to the basket, which means she didn't get credited with an assist. But overall, low assist ratios have not stopped otherwise talented centers from making the league; a short list of centers who have made rosters with low assist ratios: Ta'shia Phillips (who is right behind Alexander in the 0.2 percentile), Quanitra Hollingsworth, Kelley Cain, and Tina Charles (5th percentile). That's obviously a mixed bag, but in an 11-roster league, just making it through training camp is an achievement and Alexander even has a very good shot of ending up in someone's rotation based on her numbers.

Kelsey Bone

So that brings us to Kelsey Bone. I'm not sure everyone would rank her below Alexander, but the question after looking at her numbers is what dominant strength she has.

She's a solid, though not outstanding, rebounder, scorer. Her free throw rate is beneath that of a successful prospect in the past. Her personal foul efficiency is Her turnover ratio is right on the border of an unsuccessful prospect. But I've said it before and it bears repeating: Bone could very well defy those red flags and end up making an impact. She has all the physical tools to become a solid pro and you can imagine her succeeding in a place where she isn't the focal point of her team's offense.

Morgan Johnson

We've already been over Morgan Johnson and I won't belabor the point, but I will summarize her value as this: while she doesn't have a clear statistical weakness, there's also not a clear statistical strength. Add to that chronic knee problems and WNBA GMs could flag her as a bit of a medical risk that would hurt her chances of getting drafted. A player like Bone - even with her red flags - might just have more potential.

As for concerns about her not wanting to play basketball after graduation, it seems that was cleared up back in January. Again, she's worth a pick when you look at the roster-worthy posts available.

Carolyn Davis

Davis has been considered in the mix for a first round pick for most of the year, but the numbers don't cast her in that favorable a light.

The big thing is that personal foul efficiency, which has really been a blow to centers in the past. Like Bone, her turnover ratio approaches red flag levels and she doesn't have the assist ratio to offset that (returning to the point about Alexander's tendencies above, Davis is in the 5th percentile). Her relatively low offensive rebounding rate makes her something of a scoring center who doesn't have an outstanding scoring efficiency - the risk is whether she'll be able to contribute if she doesn't score.

If you say that scoring efficiency threshold is arbitrary and she's strong enough to succeed, then you also have to consider that the turnover numbers and personal foul numbers might be too low. Clearly her injury history has to be taken into account and maybe continued rehabilitation will happen. But for now, Davis is not the type of sure thing that a team might want in the first round.

Talia Caldwell

The rest of the centers in this draft all have some serious red flags, but Caldwell is probably the best of them: she's efficient enough of a scorer to be considered a draft-worthy player and she's an outstanding offensive rebounder. Obviously I've been saying throughout this that offensive rebounding isn't a big deal for centers - the best center prospect in this draft isn't a great offensive rebounder. But if you're looking for a factor that might help any one of those centers in the bottom half of this list compete in training camp, Caldwell's combination of rebounding and scoring efficiency might be it.

For more on the 2013 WNBA Draft, check out our draft prospects storystream.