Red Sox Deliver Another Rivalry Salvo, but Does Regular Season Record Have Bearing in October?

(The following is being syndicated from The Captain’s Blog).

If the Yankees were hoping to deliver a message to the Red Sox this past weekend, it didn’t reach the intended destination. In fact, it was returned to sender. Not only did Boston win another series, but the team beat CC Sabathia for the fourth time and then, for good measure, added a blown save to Mariano Rivera’s record. Message received…loud and clear.

The 1983 NLCS looked like a mismatch in favor of the Dodgers, but the Phillies won despite going 1-11 against Los Angeles during the regular season.

For the second time in the last three years, the Yankees started off the season series against the Red Sox by losing eight of the first nine. Unlike 2009, however, the Yankees won’t be able to turn the tables and tie the series. With a 10-2 record (.833 winning percentage) over the first 12 games, Boston has already clinched victory in its private war with the Yankees, so, from a rivalry standpoint, the remaining six games will simply determine the level of the Red Sox’ head-to-head dominance.

Despite performing so poorly against their chief rival, the Yankees are still in good position to win the division. However, with both teams well ahead in the wild card race, the urgency to claim first place could be greatly diminished. Although that fallback position mitigates concern about the Yankees’ inability to beat Boston, should the two teams meet again in October, the Bronx Bombers will be in the unfamiliar position of being a decided underdog.

When the postseason begins, the old cliché says you can throw the regular season out the window, especially regarding head-to-head performance. But, should that advice apply to the level of dominance that the Red Sox have exhibited over the Yankees in 2011?

Regular Season Head-to-Head Records by Playoff Series Winning Teams, Since 1969

Source: Baseball-reference.com

Since the advent of division play in 1969, there have been 150 intra-league playoff series. In those post season matchups, the combined regular season record of the winning team against the losing team is .518 (.531 in the American League and .505 in the National League), which suggests that head-to-head regular season play might have at least a small amount of predictive value, particularly in the junior circuit.

On an individual series basis, we find a similar result. Out of the 129 playoffs series between teams that didn’t play to a .500 record against each other in the regular season, the club with the advantage won 70, or 54.3%. Once again, the National League proved to be much more egalitarian. In the NL, the ratio was an even split, while in the AL, the team with the better record won just over 58% of the time.

Regular Season Head-to-Head Records of Individual Playoff Series Winners, Since 1969 (click to enlarge)

Note: Bars depict the number of teams to win a series after recording the defined winning percentage range against the same opponent during the regular season. Ranges correspond as they diverge from .500 (i.e., when combined, they yield total games for each segment).
Source: Baseball-reference.com

Exactly one-half of the 150 October matchups have featured teams who played a regular season series within a winning percentage band of .400-.600, which, considering most of the sample sizes, isn’t much of a spread. On the margins, however, the advantage swings more heavily toward the team with the better regular season head-to-head record. In this segment, 45 of the 75 series played were won by the dominant team (the AL rate was 65.6% and the NL rate was 55.8%).

If the Red Sox and Yankees’ season series maintains its course, a potential 2011 ALCS between the two teams would fall at the more extreme end of the spectrum outlined in the preceding chart. Ironically, however, at the very tail end of the segmentation, the trend seems to reverse. In fact, six of the 10 playoff series featuring a team that won at least 80% of the regular season games ended in triumph for the one with a losing record. Who knows, maybe the Yankees have the Red Sox exactly where they want them?

Turning the Tables: Postseason Victory Following Regular Season Humiliation

Note: Includes all teams that won a post season series vs. a team against which they had a regular season head-to-head winning percentgae of 20% or lower.
Source: Baseball-reference.com

The Yankees have won 21 of the 30 AL post season series in which they participated since 1969. Of that total, seven series were won despite having a losing regular season record against the playoff opponent (out of 12 such series). However, the Yankees have only found themselves on the short end of a series in which the team with an extreme losing record bounced back to win in October (versus the 2006 Tigers and 2007 Indians), which suggests the Yankees don’t play the roll of underdog nearly as well as favorite.

There are still six games left in the season series with the Red Sox, so the Yankees can still narrow the gap. However, thanks to the wild card, even if the Yankees aren’t able to recover from a lopsided record against Boston, the team could still get one final shot at their rival in October. In some ways, that’s a serious flaw in the current MLB playoff format, but nonetheless, that one extra chance could wind up being the only one that counts. In the meantime, the Red Sox can rest comfortably on the laurels of being the alpha dog in the A.L. East.

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