The following is the criteria that each pitcher must pass to be eligible for the ranking (there were 48 eligible) : Must currently be 25 years old or younger.
Cannot have thrown more than 50 innings in the NPB (or Ichi-Gun)
Must have thrown at least 30 innings in the Ni-Gun this year (so we can get a serious look at him statistically).
Cannot have pitched in 3 different seasons in the NPB (or Ichi-Gun). So if a pitcher is 24, and only thrown 40 NPB innings spread over 3 different years, he is left out.
So obviously we won't be including 2012 draftees. Shohei Otani is probably the guy I would rate as the best pitching prospect in the NPB, but he doesn't qualify according to this formula (just because I have no way of rating the recent draftees without finding video and information for them all).
I didn't distinguish between the Eastern League or Western League, so I used:
4.29 league average kwERA
3.22 league average FIP
To adjust this into kwERA - and FIP -, we should be able to use the same formula as we did with OPS +. For example, if a pitcher has a 4.00 kwERA, we subtract it by 4.29 (giving us -.29) then divide it by 4.29 (giving us -.0676) then add 1 (.9324) and then multiply it by 100 and round, giving us a 93 kwERA -. This is what I did for each pitcher in the spreadsheet.
For velocities, the two main sources were NPB Tracker Data and the Japanese Wikipedia (which was extremely helpful). I also used other sources, including YouTube videos, when needed.
I found it interesting that almost all the Hanshin Tigers pitchers seemed to struggle with homers (despite having solid kwERA and velocities). I wonder if their park is smaller, and I wish I had enough info to create a separate park factor for them.
For the rankings, I sorted by each category (I decided against using left-handedness as a better ranking than right-handedness, so the things we are ranking are age, kwERA, FIP, and velocity) and used the average ranking for each pitcher to sort them. The lower the number of the ranking the better. To download the spreadsheet to see the whole list, click on this hyperlink, or copy and paste the address below:
The top 5 NPB Ni-Gun pitching prospects according to the above formula, along with some video I found online and a short scouting report:
1. Yodai Enoshita
Yet another Fighters right-handed arm with a legitimate fastball, Enoshita didn't pitch in the NPB in 2012, but got a cup of coffee in 2011. He threw a slider that almost reached 82 MPH, but that was the only breaking pitch he showed according to NPB Tracker data. If you watch the video, you also see him throw some kind of splitter at around 77 MPH and he also has a slow curve. His delivery is a little complicated, and one always wonders about repeat-ability (and whether or not that makes him a reliever more long term), but it does give him some deception, as he pauses and hides the ball. Since he is 23, one would like to see him make an impact in 2013, but the Nippon Ham roster is not always easy to crack.
2. Robert Zarate
Zarate's story is unique enough that I almost didn't include him on the rankings, and it turned out that the left-hander was actually tied with Enoshita for number 1 according to the formula. At age 25, he won't be eligible next year, and he has dealt with shoulder injuries in the past. Zarate was originally signed by the Blue Jays out of Venezuela and pitched for their Dominican Summer League affiliate in 2006 and 2007, showcasing shiny ERAs, low walk rates, and solid strikeout rates. In 2008, he pitched in two Gulf Coast League games, but his minor league career ended there. However, he resurfaced with Hanshin and even pitched in 2 games for the Ichi-Gun team in 2012. He also has a high leg kick, and somewhat of a hip swivel like Felix Hernandez has in his delivery. He then comes with a 3/4 arm slot, and despite his mediocre frame, he is able to generate plus velocity.
3. Ryuji Ichioka
The Giants right-hander has a more exaggerated version of Enoshita's delivery with an extreme pause. His breaking pitch has some good movement at 80-81 MPH, but his control of it seems to be mediocre. If hitter's reactions are any indication, his combination of okay velocity and movement of his two pitches seem to be at least adequate in getting hitters out. To have the amount of success the other pitchers on the top 5 can have, he will have to show superior command as his stuff and velocity is not quite as sharp as theirs.
4. Ryoma Matsuda
Another Tigers' pitcher, Matsuda held his own as a teenager in the Ni-gun thanks to a good fastball and the ability to hide the ball despite the small frame. The arm action scares me a little, but there is a chance he could get a little bigger and add some more velocity. If not, he could still be a very nice relief pitcher, as the ability to hide the ball would play better in short spurts.
5. Shohei Tsukahara
Even without a plus fastball (but it is not like he has a bad fastball), Tsukahara was pretty dominant in the Ni-Gun in a short sample size. He still has some projectability as a 20 year old thanks to his somewhat long slender frame. His delivery is relatively standard by Japanese standards, and he takes a nice long stride.