Looking at Depth Ratio for Northwestern

Depth is important in college basketball, or at least that’s how the old adage goes. Teams can’t win if they’re not deep and have talented players coming off the bench. Yet the Northwestern Wildcats continue to challenge this maxim. It turns out Northwestern almost always has its best seasons when using the least depth – at least under Bill Carmody.

For this analysis I’ve used something called Depth Ratio. This was created by K.J. over at the Michigan State blog The Only Colors. It’s baffling simple to calculate, but it seems to lead to some really power analysis. Over the next week or so I’m going to be tackling DePaul (both Wainwright/Webster and Purnell), Loyola and UIC.

Every post though is going to use this simple formula: Depth Ratio = (minutes of top two players) / (minutes of 8th and 9th players). If you want to read more about it in relation to Michigan State and the ideas behind it check out here and here.

Michigan State’s “magic number” under Tom Izzo is apparently 3.00. That’s where the team has enough depth to be competitive. Depth is important for the Spartans, it’s not for the Wildcats. More analysis as to why after the jump.

Northwestern’s average depth ratio the past 12 seasons has been 3.71. It is only when that number gets over 4.00 that the Wildcats become competitive. Yes, the top two starters need to be playing almost four times as much as the third and fourth guys off the bench for Carmody’s system to be effective. And I have some theories as to why.

Theory 1: The Princeton Offense is hard to learn – Northwestern under Carmody plays an offensive set that is hard to learn and difficult to master. It relies on a lot of things – like talented three-point shooters – but the biggest is chemistry between players. Each player needs to know where the other players are going to be on the court, because otherwise all those backdoor cuts are worthless. This chemistry means that a group of players that play consistently together are going to run the offense much more effectively than a team that’s constantly rotating players.

For example: Northwestern’s 2009-10 season – the best under Carmody according to RPI – came with a depth ratio of 4.44. The two worst seasons in the past 12 are 2008-09 – depth ratio of 2.55, and 2000-01 – depth ratio of 2.06. This brings me to theory number two.

Theory 2: Northwestern recruiting hasn’t allowed for talent deep into the bench – It is no secret that the Wildcats have had some problems recruiting under Carmody. Current success not withstanding Northwestern typically brings in the lowest or second lowest rated class in the Big Ten. These classes tend to be composed of one good to very good player – Kevin Coble, John Shurna, Drew Crawford, etc. – and then some other pretty good players. It’s those pretty good players that are overmatched. Thus when Carmody shortens the bench those players aren’t exposed as much and the team plays better.

Finally, there’s a reason that shortening the bench works for Northwestern and it’s this:

Theory 3: The tempo Northwestern plays at doesn’t requires as much depth – The Wildcats are always one of the slowest paced teams in the country. Because of this, every possession is a very high leverage situation. You have to have your best players on the court. Thankfully, Northwestern can do this because players aren’t sprinting back and forth. The best example of this I can site is last season’s game against Wisconsin at Welsh-Ryan Arena. Look at the box score. Five players total got of the bench for the two teams and they played a combined 30 minutes. Bo Ryan and Bill Carmody knew the importance of every possession in that game.

So sure, everyone thinks that depth is important, and maybe over a season it might be nice if Juice Thompson didn’t have to play 34 minutes in a home victory over North Carolina A&T, but overall depth isn’t the crutch common sense may lead you to believe.

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