Wei-Yin Chen | Baltimore Orioles | SP | Signed as International Free Agent
The Orioles have displayed a huge fascination with Asian pitchers this offseason. They inked Tsuyoshi Wada to a major-league deal last month, Eun Chul Choi to a minor-league deal earlier this month, dabbled in the Hisashi Iwakuma sweepstakes, and nearly signed Korean pitcher Chong Tae-Hyon before he decided to stay in Korea at the last minute. This week, the O’s signed pitcher Wei-Yin Chen.

The Numbers
Chen is a 26-year-old Taiwanese-born pitcher who has pitched in Nippon Pro Baseball for the past several seasons and holds some nice upside, but not without comparable risk. Chen’s numbers fell off this season, even after accounting for the new ball that Nippon Pro Baseball put into effect. Chen’s Central League, as a whole, saw an ERA drop of 20 percent (slightly less than Yu Darvish’s Japanese League), due in large part to a huge home-run drop (just like we saw in the JL):

NPB CL Changes in League Average from 2008-2010 Three-Year Average to 2011











Seeing how the league-average pitcher has been affected, we can now look at how Chen’s stats compare to a league-average pitcher’s in each of his seasons. The table below displays data in the form of percentage better than average (so in 2008, his ERA was 29 percent better than the league-average pitcher, and his walk rate was three percent worse):

Wei-Yin Chen’s Stats as Percentage Better than Average































We see that, in general, Chen pitched significantly worse this past season than he did from 2008 to 2010. Despite the league as a whole actually slightly increasing strikeouts with the new ball, Chen’s strikeout rate dropped off precipitously, to the point where he was actually 23 percent worse than a league-average pitcher in 2011. He compensated a bit by cutting down on the walks, but his home-run prevention was well below his 2008-2009 levels, and his ERA followed.

Scouting Chen
Since Chen’s 2011 struggles clearly can’t be pinned squarely on the new ball, what actually happened to him? The biggest concern is with his strikeouts, and scouts I spoke with say that his stuff was significantly diminished this past season, supposedly due to injuries to his groin and hamstring. Over at ESPN, Keith Law said that Chen’s season was a tale of two halves, where he showed lowered velocity and a slider that lacked bite early in the season, but got some of it back by the end. Law reported that Chen’s fastball sat 88-92 mph early on, but was back up to 92-94 by the end of the season. Patrick Newman’s NPB Tracker corroborates this to an extent, placing Chen’s average fastball in the 88-89 mph range (touching 92) early in the season, but still only averaging around 89-90 by the end of the season (touching 94). One scout I spoke with said that Chen would consistently sit in the 91-95 mph range prior to 2011, and it doesn’t appear he got all the way back there even by the end of the year.

Like Law, this scout said that Chen’s slider used to be a very good pitch, and noted that it was much softer this season. Going back to NPB Tracker, we do see that Chen’s slider averaged around 85 mph in 2010, but averaged just 80-82 this year. His slider’s velocity did not return by the end of the season (actually, over his last few starts, it dropped to the 78-80 range).

Chen’s fastball velocity started bouncing back around his 22nd start, at which point his strikeout rate did begin to prop itself up. He still wasn’t near where he was in previous years, and of course we’re dealing with a small sample size, but it’s worth noting.



% Above Lg. Avg.*

Starts 1-20



Starts 22-27



*Note that I use the league average for the entire season, not for the timeframe in question, which could make a difference if things like weather affect the league average in Japan at different times of year.

Summing Up
If Chen’s drop-off in stuff was indeed caused by the groin and hamstring injuries, he could offer the Orioles and fantasy owners who gamble on him quite a bit of upside. He’s no Darvish, but Chen could definitely be better than Tsuyoshi Wada. He still has plus control and can strike batters out when his stuff is right, so it will be important to see how Chen looks in spring training. The usual Japan-to-America caveats apply, but Chen could be an interesting upside pick in the late rounds of an AL-only draft, especially if you have the benefit of drafting in the second half of March, when we know what he’s bringing to the table. The influx of Japanese pitchers this season might help Chen float under the radar, as fantasy owners might see so many of them, discount them as interchangeable, note how non-elite Japanese pitchers have struggled in the US, and place a low value on all of them not named Yu Darvish.  

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You mentioned the effect of the different baseball in the league, and I have to admit that I'm wondering if a lot of MLB teams are getting sucked in by the effect and overestimating their projections for these players. Has anyone done any work on trying to translate some of these leagues #'s to effective mlb projections yet?
Yes, most projection systems have some sort of translation system, PECOTA included. They're not as reliable as straight MLB data, of course, but they are getting better with each new data point we receive (i.e. a Japanese player jumping to America or visa-versa).