Who is Wei- Yin Chen?

The Baltimore Orioles’ rotation was a disaster in 2011, ranking dead last in the major leagues in innings pitched, ERA and FIP as highly-touted young arms like Brian Matusz and Chris Tillman crashed and burned. The O’s and new GM Dan Duquette signed Japanese starter Tsuyoshi Wada last month, and now they’re looking to the Far East for another lefty in hopes of improving those dismal numbers in 2012, signing Wei- Yin Chen of Nippon Professional Baseball to a three-year contract.

Born in Taiwan, Chen pitched the past four years for the Japanese Central League’s Chunichi Dragons but had an opt-out clause in his contract that allowed him to become a free agent at age 26. Now that he’s coming stateside, what can we expect from Chen? Let’s take a closer look at his stuff and stats.

Chen has more of a drop-and-drive delivery commonly seen in the majors, as opposed to the hesitation present in the motion of pitchers like Daisuke Matsuzaka and Hiroki Kuroda. At his best, Chen has reportedly sat in the low-90s with his fastball while mixing in mid-80s sliders and forkballs and some slower curveballs. ESPN’s Keith Law ranked Chen 19th on his top 50 free agents list, saying Chen “offers more upside than the typical NPB refugee, both due to age and the chance for the slider to become a consistently plus pitch.”

While Chen is young and has a promising fastball/slider combo, his stuff was down in 2011. Pitch data from Patrick Newman’s NBP Tracker website shows that Chen’s heater sat in the upper-80s until around July, at which point he gained some zip and more often sat in the low-90s. His slider didn’t seem to recover as quickly, as the pitch sat in the high-70s for most of the year.

Chen apparently dealt with a leg injury in 2011, which could explain his velocity dip. Whatever the cause, this past year was his worst in Nippon Professional Baseball. I found Chen’s 2008-2011 stats from Baseball-Reference and then compared them to the league averages for each season. It’s always good to provide context, but this is especially important because NPB switched to a smaller, smoother baseball in 2011 that put a huge dent in offensive production.

Teams scored between 3.9 and 4.3 runs per game from 2008-2010, but just 3.15 runs in 2011. That means there’s a higher threshold for pitchers to truly stand out, and numbers that might have looked good in past years are run-of-the-mill in last year’s run environment. To account for that, I put Chen’s strikeouts, walks, home runs and ERA on a scale where 100 is average and above 100 means the pitcher was better than the league average.

Chen appears to have become a markedly different pitcher since he debuted at age 22, cutting his walks considerably and being stingy with home runs but also seeing his K rate plummet to way below the league average (26 percent below in 2011). The result was an ERA that was a modest 14 percent better than that of the average Japanese Central League pitcher:

Wei- Yin Chen’s Japan Central League Stats
Year	IP	K/9+	BB/9+	HR/9+	ERA+
2008	114.2	125	96	180	129
2009	164	118	123	180	231
2010	188	107	130	100	144
2011	164.2	74	159	120	114

Chen’s fantasy value is hard to gauge. He would have garnered much more interest a couple of years ago, when he sported a power fastball/slider arsenal and did a good job of both missing bats and limiting walks. Now, he looks more like an extreme control pitcher with a less-sinister repertoire. That’s not to say that Chen can’t regain his lost stuff and start striking out hitters again (his fastball velocity did creep back up late in 2011), but that four-year K decline isn’t a positive sign.

While we implore people not to take spring training performance as gospel (small sample sizes and drastically different levels of competition make the numbers fuzzy at best, useless at worst), you’ll have to do your homework on Chen to get a better read on his value. Do his fastball and slider look sharp? Do hitters have a hard time picking up his motion? Is he guaranteed a starting spot? Don’t write him off if he gets crushed for a 6.00 ERA in Grapefruit League action or start thinking he’s an ace if he puts up a 1.00 ERA, but it’s important to keep up with Chen’s performance and see whether his stuff has recovered. The 2011 version of Chen won’t help you, but the 2008-2010 version could.