Ichiro, All-Time Hits King*(?)

Ichiro, in a pose that I hope one day is preserved as a statue somewhere in Safeco Field.

Ichiro is having himself a fine season with the Miami Marlins. He finds himself up to 2,979 career MLB hits and seems nearly certain to get 3,000 this season (likely sooner rather than later). More significantly, Ichiro just passed Pete Rose for the most hits ever by a professional baseball player if his hits in Japan are included with his MLB stats.

Understandably, there are divided opinions on whether Ichiro's Japanese league hits should count or not. Shockingly (note the sarcasm) Pete Rose doesn't think they should. His argument is essentially the age-old "slippery slope" one: the Japanese leagues are not the same caliber as MLB, so where does the line stop? Should Rose's minor league hits count then? What about Negro League stats?* If Japanese stats are included, our record books live in an entirely new world.

*Editorial note: those should totally count, and it would be a worthy challenge to try to translate those to Major League equivalencies.

Rose is obviously biased, especially given that the hit record is all he has thanks to his banishment from baseball for gambling. I am obviously biased too, given that I am a Mariners fan and watched Ichiro's prime up close. Still, even I can admit that Rose has a valid point. I think he is asking the wrong question though. The Japanese leagues are strong, but not as strong as Major League Baseball. That is not the real question at the heart of this debate between Ichiro and Pete Rose.

Who is the true hit king? And how do we figure that out?

I, for one, propose a different investigation. What if Ichiro had played his whole career in Major League Baseball? How different would his hit total be?

Obviously, we can never know for certain how different Ichiro's career would have been if he played his whole career in Major League Baseball. However, we have seven full seasons of data in Japan (plus a couple cups of coffee early on) and over a decade of data in MLB to look at. This is enough to make some educated guesses on.

So, I made some educated guesses. This whole next section is about my method. You can skip it if you want to avoid the details underneath the hood and go straight to the results (look for the next bold headline) if you prefer.

Translating Ichiro's Japanese hits into MLB equivalencies

Simply translating hits would be a pretty sloppy way to make the jump from Japan to MLB. Really at the heart of the transition is the quality of pitching and how Ichiro responded to it. There is at least a belief that MLB pitchers are quite a bit better than Japanese pitchers as a cohort. Better pitchers tend to strike out more batters, issue fewer walks, and/or induce weaker contact.

So, I chose to look at five stats: plate appearances (PA), walk percentage (BB%), strikeout percentage (K%), home run percentage (HR%) and batting average on balls in play (BABIP). Plate appearances log how many times Ichiro steps to the plate (walks and at-bats together). BB%, K%, HR% and BABIP all describe outcomes at the plate: either Ichiro walked, struck out, hit a home run, or put the ball in play somewhere. This is as true in MLB as it is in Japan. The real trick is figuring out how these factors changed when Ichiro faced MLB pitching. We would see evidence both of better pitching and any strategic adjustments Ichiro made within these numbers. Finding the conversions, and then using those conversions to adjust his Japan numbers, would give a good idea how Ichiro's seasons would have translated in MLB.

The other reason to use these underlying numbers is that they all stabilize relatively quickly. Fangraphs sample size suggestions say that BABIP of all these numbers is the most unstable, and the only one which would not stabilize within the confines of one season. The same could not be said for many other statistics. Eliminating noise in the data by picking stats that stabilize the quickest should help with accuracy.

Lastly, I decided to consider sample size anyway. I took all seven of Ichiro's full seasons in Japan but weighted them with his age 26 season worth 1, 25 worth 1/2, 24 worth 1/3, and so on until his age 20 season was worth 1/7. I went through the same process with his first 7 seasons in MLB, though with his age 27 season worth 1, age 28 worth 1/2, age 29 worth 1/3, and so on. Essentially, my assumption is that we really want to find the conversion between his age 26 and 27 seasons and use that to gauge as best we can how the rest of his Japanese seasons would have unfolded if they had happened against MLB pitching. Ichiro no doubt developed over his time (both in Japan and the United States), but he also had some up and down seasons. Including multiple years, but weighting them in the way I did, is an attempt to have neighboring seasons inform the investigation without obscuring that the most important and helpful data is closest to when Ichiro made the transition.

With the conversions for all five stats, it is easy to reverse engineer Ichiro's estimated hit total. I took Ichiro's plate appearances and multiplied them by 1.2 to account for the MLB season, which is approximately 20% longer than the Japanese regular season. I then took Ichiro's BB%, K%, HR%, and BABIP for each Japanese season and adjusted them according to the conversions I found based on his numbers in Japan versus his numbers in MLB. Then, with these four rate stats altered, I went back to his projected plate appearances and extrapolated how many walks, home runs, at-bats, and most importantly, hits he would get.

Results

First of all, the conversion rates I found with my method of investigating Ichiro's statistics confirmed that Japanese pitching is not as strong as MLB pitching, and that there is a noteworthy gap. I estimated that Ichiro's walk rate sunk about 37%, strikeout rate rose 18%, home run rate dipped 64%, and BABIP rate sunk 13% when he transitioned from Japan to MLB. In other words, pitchers walked Ichiro less while also striking him out more and inducing weaker contact (given that he hit way fewer home runs and less balls in play went for hits). These are strong indicators across the board that MLB pitching was a noteworthy step up for Ichiro.

Here are Ichiro's Japanese numbers, adjusted for MLB competition based on how he transitioned to MLB:

Age	| Jpn PA	Jpn AVG	Jpn HR	Jpn Hits	| MLB PA	MLB AVG	MLB HR	MLB Hits
18	| 99	.253	0	24	| 119	.216	0	25
19	| 67	.188	1	12	| 80	.168	0	13
20	| 616	.385	13	210	| 739	.345	6	242
21	| 613	.342	25	179	| 736	.321	11	220
22	| 611	.356	16	193	| 733	.323	7	223
23	| 607	.345	17	185	| 728	.316	7	215
24	| 558	.358	13	181	| 670	.323	6	206
25	| 468	.343	21	141	| 562	.324	9	171
26	| 459	.387	12	153	| 551	.352	5	179

The results are fairly interesting, and counterintuitive at first. Clearly, Ichiro's batting suffers against MLB pitching. His projected batting average dips 20-30 points every year and his projected home run totals plummet. However, his projected hit totals increase.

This counterintuitive result is largely driven by the longer MLB season, and more directly the assumption that Ichiro would be playing every day. However, the only reason that matters is because of how all the other factors combine.

Ichiro's shrinking walk and home run rates, while harmful to his overall value as a hitter, actually helped him more than offset his increased strikeout rate. Simply put, overall, Ichiro put more balls in play in MLB than he did in Japan because he walked so much less and hit so many fewer home runs that they more than offset his elevated strikeout rate. All three of these factors take balls out of play, and the main driver of how many hits a player gets is how many balls they put in play. Moreover, while Ichiro's BABIP shrunk some, it did not shrink a ton. The net result is a relatively similar hit rate extended over a longer season. In fact, I project Ichiro would have over 200 more hits if he had played in the majors - 1,494 projected hits to his actual 1,278.

There is one last big catch though that's pretty impossible to answer: when would Ichiro have debuted in Major League Baseball? He almost certainly would not have played as an 18 or 19 year old, especially given his struggles. 20 years old is also very young for a player to debut, much less start a whole season, but Ichiro's age 20 season was arguably his best in Japan. 20 isn't so ridiculously young to think Ichiro couldn't have made the majors at that age, especially given that he is a Hall of Fame talent and that he performed at such a high level in Japan. However, there really is no way to know.

If Ichiro had debuted playing every day as a 21-year-old, I have him projected at 4,193 total hits if he played his whole career in MLB. That would be less than 100 hits short of Pete Rose. So, if Ichiro had debuted halfway through his age 20 season and performed as well as he did, then he would theoretically have the all-time hit record. It's certainly plausible that Ichiro could have done this. Is it probable that he would have though? Hard to say, maybe even impossible.

Of course, this all assumes that Ichiro doesn't get another hit in MLB, and he isn't done yet. He is likely to collect several more hits between now and the end of his career. The more he gets, the later he would have to debut to be the all-time hit king with my projection method.

So, is Ichiro the new all-time hits king? It's hard to say. If he isn't, he is darn close. He is most certainly in a realm only Ty Cobb and Pete Rose have entered before him. That's ultimately the whole point in my eyes.

Ichiro's hit total tells a story; it says something about who he is and what a marvel he is when he steps into the batter's box. History suggests that there will be another hitter something like Ichiro at some point, but hitters like him are exceedingly rare, not even once in a generation. There is no guarantee we see another hitter like Ichiro in our lifetimes. That's what his Japanese numbers help us see and appreciate. That's the real story here. Long live Ichiro.