Phillies vs. Reds
Roy Oswalt: 2.76 ERA, 3.33 SIERA
Oswalt joined the Phillies in late July and posted a 1.74 ERA in 12 starts and an inning of relief. The Phillies won 10 of his 12 starts, but his SIERA of 3.33 was a dead ringer for his 3.31 SIERA in his 20 starts with the Astros. Oswalt’s .227 BABIP with the Phillies was due to very few ground balls finding holes and outfield flies staying catchable more often than can be expected in the future. However, both his 2010 SIERA in Philadelphia and in Houston were far better than his recent years’ SIERAs of 3.89, 3.63, and 3.86 from 2007-09. The reason is that Oswalt struck out more hitters than he had since his 2001 rookie year, raising his strikeout rate from 18.2 percent in 2009 to 23.1 percent in 2010. Oswalt began using his changeup more in 2010 with the Astros early on, and began using it even more after working with Phillies pitching coach Rich Dubee. Thus, Oswalt has the sixth-best SIERA among all starters in the playoffs and 13th overall, after finishing only 33rd in the majors in 2009.

Bronson Arroyo: 3.88 ERA, 4.66 SIERA
Arroyo has managed to put up ERAs of 3.84 and 3.88 the past two years, but a good deal of luck has factored into both, as he has been declining for several years now. His strikeout rate has only been 13.8 percent in each of the last two years, decidedly below the major league average of about 17.6 percent for starting pitchers. He has a solid 6.7 percent walk rate, though his batted-ball rates are pretty average all around. Arroyo is nowhere near the second-best starter on the Reds but was been given the nod for Game Two anyway. In his career, he has struggled against lefties, with a 3.0 K/BB vs. RHB and only a 1.5 K/BB vs. LHB and an 816/684 OPS split as well. This year, his .192 BABIP vs. RHB has exacerbated his OPS split to 786/576 for 2010. Lefties like those in the heart of the Phillies’ lineup are going to have a good chance against Arroyo.

Giants vs. Braves
Tommy Hanson: 3.33 ERA, 3.74 SIERA
Hanson lowered his walk rate from 8.8 last season to 6.6 percent in 2010, but also lowered his strikeout rate from 22.2 to 20.5 percent and was left an almost identical SIERA. Hanson is neither an extreme ground-ball pitcher nor an extreme fly-ball pitcher, so his command of the strike zone is the key to his success. He has had ERAs below his SIERAs in his first two major league seasons primarily due to low home runs per fly ball rates. His 9.5 percent was below the league average of about 13.1 percent as a rookie but this year it dropped to 7.2 percent, which was well below the league average of 12.3 percent. Thus, Hanson has beaten his SIERA two years in a row. His .279 BABIP in 2009 helped as well, though his .290 BABIP in 2010 seems in line with his skill level as a power pitcher who is not much of a ground-ball generator. If Hanson is going to repeatedly beat his SIERA, it will be because he can keep his HR/OFB low, but pitchers who maintain lower than usual rates in that area also tend to generate a lot of infield pop-ups. That is something Hanson is pretty good at doing, but not amazing. In 2010, the league average was about 7.5 percent and Hanson was at 8.8 percent. I think that Hanson’s skill level is probably closer to his SIERA, but a couple more years could change my mind.

Matt Cain: 3.14 ERA, 3.90 SIERA
It’s finally time to admit that DIPS metrics like SIERA do not work well for Cain. They are bound to work for the vast majority of pitchers, but some will be the exception to the rule. However, one must be careful not to stick a feather in the cap of every rookie who beats his SIERA, and then not fall victim to confirmation bias for those who have a second year of beating their peripherals. There will be a handful of pitchers that are lucky two years in a row and appear to have SIERA-beating skills but really do not. However, it is now four years in a row with Cain. After posting a 4.15 ERA in 2006, just above his 4.03 SIERA, Cain has transformed into a pitcher that pitches ahead of his peripherals by quite a large margin. In 2007, he had a 3.65 ERA and a 4.20 SIERA; in 2008, he had a 3.76 ERA and a 4.23 SIERA; in 2009, he had a 2.89 ERA and a 4.09 SIERA; and in 2010, he had a 3.14 ERA and a 3.90 SIERA. None of these are bad SIERAs. Cain strikes out 20 percent of hitters and walks only 6.8 percent. He is by no means a ground-ball wizard, but he induces pop-ups pretty regularly (11.4 percent of balls in play in 2010) suppressing his BABIP. His BABIP in his career is .270, and his HR/OFB is just 9.6 percent. Chances are that Cain has been a little bit lucky in this string of SIERA-beating ERAs, if for no other reason than it seems almost impossible that he was unlucky. However, Cain is one of the better pitchers in the postseas and gives the Giants a solid one-two punch with Tim Lincecum with which to compete against the NL’s best.