Lefty Wei-Yin Chen takes the mound for the O's tonight, down 2-0 in the series to the Royals. How have Royals' hitters fared against similar pitchers?

The Baltimore Orioles find themselves in a precarious spot, down two games to the Kansas City Royals with the series picking up in Kansas City tonight. The Royals were able to win the first two games of the series on the road, and now itâ€™s Baltimoreâ€™s turn to try and win away from the comfy confines of Camden Yards and prolong the series.

The Oâ€™s were a very good road team this season, as their 46 wins away from Baltimore were bettered by just two teams in baseball, the Los Angeles Dodgers andâ€¦the Royals. Itâ€™s technically not a â€œmust-winâ€ game for the Oâ€™s, but in order to avoid having to win four games in a row, they must win tonight. And starting on the mound is Baltimore lefty Wei-Yin Chen.

Chen's Arsenal

Chen has relied primarily on a four-seam fastball this season, with an average velocity of just under 93 mph, and heâ€™s thrown this pitch over half of the time - 52.23% to be exact. Check out the table below for a breakdown of the remainder of Chenâ€™s repertoire. (Numbers courtesy of Brooks Baseball.)

Pitch Type Frequency Velo (mph) Four-Seam 52.23% 92.93 Slider 15.61% 83.15 Sinker 13.56% 92.23 Split 11.45% 84.55 Curve 6.90% 74.86

After Chenâ€™s fastball, he uses a mix of sliders, sinkers, and split-fingers, with the occasional curve added in. Chen isn't the type of pitcher to consistently blow a pitch by you, and relies rather on his above-average control to keep hitters off balance. His strikeout-to-walk ratio of 3.89 was good for 21st-best among qualified starting pitchers this season.

Can the Royals Hit Him?

Now that we know what Chenâ€™s pitch selection is, letâ€™s see how Royalsâ€™ hitters have performed this season against similar pitches (numbers via Baseball Savant.)

Kansas City has five batters out of their starting nine who hit .341 or better against four-seam fastballs thrown by lefties this season, with two players - Nori Aoki and Lorenzo Cain - hitting over .400. The only player in the first six spots of the Royalsâ€™ lineup not to hit .341 or better is cleanup hitter Eric Hosmer, who hit .253. Simply put, the Royals have hit lefty fastballs very well this year.

Chenâ€™s next most frequently thrown pitch is his slider, and luckily for him, the Royals have had far less success hitting lefties throwing this pitch. No hitter in the Royalsâ€™ starting lineup has hit above .250 against lefty sliders this year, with the top of the order, Alcides Escobar and Aoki, hitting the worst at just .118 and .053, respectively. If Chen is able to find success tonight, it could be because of his slider. The sample size for lefty thrown sinkers and split fingers that the Royals have faced this season are too small for any significance, so letâ€™s move on to Chenâ€™s curve.

The Royals have hit lefty curves fairly well this season, with four of their regulars batting .300 or better against them, and Aoki leading the way hitting .353. Hosmer, again, struggles in this category as he has hit just .158 against lefty curves. If Hosmer is up in a big situation, the numbers suggest that Chen should attack him, especially since Billy Butler bats after Hosmer and has hit lefties well this season.

These numbers are against lefties throwing pitches at any velocity, but letâ€™s see how they compare to lefties throwing these pitches at similar velocities to Chen to get a better idea of how the Royals have fared against similar pitchers. Since four-seam fastballs and sliders are the two pitches that Chen throws the most and that we have the largest sample size for in this scenario, I used them to create this table comparing the Royalsâ€™ batting averages against lefty pitches of any velocity, as well as those versus velocities similar to Chenâ€™s. The table reflects the lineup used by the Royals in every playoff game so far.

Hitter Any FB FB <93 Any SL Slider <85 Escobar .391 .417 .118 .100 Aoki .429 .432 .053 .000 Cain .419 .400 .222 .313 Hosmer .255 .125 .235 .381 Butler .372 .313 .250 .143 Gordon .342 .333 .150 .150 Perez .139 .167 .214 .375 Infante .243 .194 .250 .200 Moustakas .200 .143 .158 .231

In order to get a â€œtruerâ€ comparison, I used Chenâ€™s average velocity for each pitch - fastballs 93 mph and less and sliders 85 mph and less. (I realize that â€œaverageâ€ means he throws pitches harder than these numbers, so itâ€™s not a perfect comparison, but I didnâ€™t want to include pitches above his average velocity for comparison sake.) The sample size becomes much smaller when adding in a specific velocity, so keep that in mind. The batting averages against fastballs are roughly the same, whereas they improve for several hitters against sliders, but again, this could just be attributed to sample size.

Chenâ€™s predominant pitch in any count is his fastball (throwing it around 53% of the time in all counts) and he relies on spotting it where he wants to, something he will need to do in order to win tonight. However, when lefty hitters were ahead in the count this season, Chen threw his fastball 66% of the time, meaning Aoki and Alex Gordon would be wise to try and work the count in their favor before attacking the inevitable fastball.

The Royals have hit lefties well this season (their .266 team batting average was good for fifth best in the AL), so I expect them to continue their success tonight against Chen. But the way the playoffs have gone so far, what happened in the regular season doesnâ€™t seem to mean anything.