Inter-League Play, Does it Effect League Winners?

*** The following excerpt is taken from a SABR, Society for American Baseball Research, Internet discussion group and discusses the impact of Inter-League play on Divisional winners. Have any of the races been affected by Inter-League play? This article is reproduced with permission of its author, James Vail, and we would like to thank him for allowing us to do so.


Inter-League Play and Post Season Qualification
by
James Vail

In the period since inter-league play began in 1998 there have been seven instances in which it might be argued that the comparative results of inter-league competition directly determined the outcome of various divisional races. Of course, it can always be argued as well that each of the outcomes displayed below would've been different if the second-place teams had only played better against in-league competition. Regardless, the seven incidents include the following.

1999 NL CENTRAL: Houston finished at 97-65 (.599), Cincinnati at 96-67 (.589), 1.5 games back. The Astros played 15 inter-league games, going 12-3 (.800), while the Reds played 12 games against AL competition, going 2-10 (.167). So, in NL-only games, Cincinnati was 89-59 (.601),good enough for a 3.5-game lead over Houston's 85-62 (.578). Houston's five inter-league opponents were the clubs in the AL Central, who combined for a 1999 record of 368-437 (.457). Cincinnati did not play the White Sox, but did play Detroit, KC, Minnesota and Cleveland, who combined for 293-351 (.455), so there was little difference in the relative strength of their inter-league schedules.

2000 NL EAST: Atlanta won the division at 95-67 (.586), one game ahead of New York, 94-68 (.580). The Braves were 11-7 (.611) in inter-league play, the Mets were 9-9 (.500). So New York was 85-59 (.590) against the NL, Atlanta was 84-60 (.583), one game worse. The Braves' inter-league slate included six home-and-away games against Boston, plus three against each of the other four AL East clubs. The combined record for those teams in 2000 was 398-410 (.493), or 483-487 (.498) if you count Boston's mark twice (because they played twice as many games against Atlanta as the others). The Mets played the same five clubs,with the only difference being that they had a 3-home,3-away series against the first-place Yankees instead of Boston. So the strength of their inter-league schedule was either identical to Atlanta's, or 485-484 (.501) if you count the Yanks twice.

2000 AL EAST: NY won the division at 87-74 (.540), with Boston second at 85-77 (.525). The Yanks were 11-6 (.747) in inter-league play, the Red Sox 9-9 (.500). So both teams finished with identical AL-only marks of 76-68 (.528). Their inter-league schedules were essentially the reciprocal of the Braves-Mets that year, with both clubs playing the full NL East, the Yanks playing six games against the Mets and the Bosox with six against Atlanta. The NL East teams combined for a 400-409 (.494) mark. Counting the Mets twice, that equates to a 494-477 (.509)against the Yankees. Counting Atlanta twice gives Boston opponents a 495-476 (.510) --- essentially a wash equity-wise.

2001 NL EAST: Atlanta won the division at 88-74 (.543), with Philadelphia second at 86-76 (.531). The Braves went 9-9 (.500) in inter-league play, the Phillies 7-11 (.389). That gave them identical 79-65 (.549) records against NL-only opponents. Atlanta played the same inter-league slate as in 2000, with six games against Boston, three apiece against the rest of the AL East. The Phils also played all five AL East teams, with their six-game, home-away set against Baltimore. The AL East that season played at 382-424 (.474) overall. Counting Boston tice gives Atlanta's inter-league opposition a 464-503 (.480) mark, while counting Baltimore twice puts the Phils' opponents at 445-522 (.460). So Philadelphia missed a chance to take advantage of a 20-point advantage in inter-league strength of schedule.

2001 NL CENTRAL: Houston and St. Louis tied for the division lead at 93-69 (.574) each, with the Astros awarded the division title based on tie-breaker criteria and the Cards earning the playoff wild-card. Houston was 9-6 (.600) in inter-league play, St. Louis 8-7 (.533). So the Cards had an NL-only record of 85-62 (.578) that was one game better than Houston's 84-63 (.571). Houston's inter-league slate included three games each against Cleveland, KC and Minnesota of the AL Central, plus a 3-home, 3-away series against AL West Texas. The Cards' played three games each against all five AL Central clubs, including the White Sox and Detroit. Houston's opposition played to a 314-334 (.485) mark, or 387-423 (.478) if you count Texas twice. St. Louis' inter-league opposition went 390-420 (.481). So the strength of their inter-league schedules was about equal, and which team enjoyed a small advantage depends on how you weight the Astros-Rangers series.

2002 NL WEST: This one is much more interesting. Arizona claimed the division title at 98-64 (.605), with SF second at 95-66 (.590), 2.5 games back. The D-Backs were 11-7 (.611) in inter-league play, the Giants 8-10 (.444). So SF's NL-only record of 87-56 (.608) was actually one-half game better than Arizona's 87-57 (.604). The D-Backs'
inter-league slate included three-game sets against four AL East clubs Baltimore, Boston, NY and Toronto) plus two AL Central teams (Detroit and Cleveland). The Giants also played the Orioles, Yankees and Toronto, but had a three-game set against Tampa Bay and a six-game, home-away series with cross-bay rival (and first-place) Oakland.

The two clubs' common inter-league opponents (the Yanks, Jays and O's) combined for a record of 248-237 (.511), and the separate, three-game series against Detroit (56-106) and Tampa (55-106) were essentially a wash. Both teams went 4-5 against their common IL opponents and 2-1 against Det-TB. So the difference in their inter-league marks came down to Az-v-Bos/Cle and SF-v-Oak. Arizona was 2-1 against the Indians and somehow swept the Red Sox at Fenway. SF could do no better than 2-4 against the A's. The D-Backs' inter-league opponents combined for an overall mark of 471-500 (.485). The Giants' opposition was 406-402 (.502), or 509-461 (.525) if you double-count Oakland. There seems to be little doubt in this instance that the inequity in the two clubs'
inter-league schedules (a 38.5-game difference when the A's are counted twice) was the determining factor in which team won the division. The irony, of course, is that SF claimed the wild-card spot anyway and then beat Atlanta, Arizona was eliminated by St. Louis in the NLDS, and the Giants went on to the World Series.

2002 AL WEST: Oakland won the division at 103-59 (.636), with Anaheim second at 99-63 (.611), four games back. Oakland posted an inter-league record of 16-2 (.889), the best-ever single-season mark to date for inter-league play (Atlanta's 15-3, .833 that same year ranks second-best). The Angels were 11-7 (.611) in inter-league games, exactly matching their full-season and AL-only percentages. The net result was that Anaheim's AL-only record of 88-56 (.611) was one game better than Oakland's 87-57 (.604). Beyond their six-game, home-away series against SF, Oakland's inter-league opponents included NL Central clubs Cincinnati, Houston, Milwaukee and Pittsburgh (three games each). Anaheim played a six-game, 3H-3A set against Los Angeles, and three games apiece against Cincinnati, Milwaukee, Pittsburgh and St. Louis.

So they shared three common IL opponents that combined for a 206-279 (.425) season record. Adding the Giants and Astros to the Oakland ledger gives their inter-league opposition an overall mark of 385-423 (.476), or 480-489 (.495) when SF is counted twice. Including St. Louis and the Dodgers in the Anaheim slate gives the Angels' inter-league opponents a record of 395-414 (.488), or 487-484 (..502) with LA double-counted. So Oakland benefitted from an inter-league slate that was either .012 or .007 easier than Anaheim's, but hardly enough to explain its five-game edge versus the Angels in inter-league play.

In addition to those seven instances, there have been two occasions when it could be argued that inter-league play determined the outcome of wild-card races. They include:

1999 NL: The Mets finished at 97-66 (.595) to claim the wild-card by a one-game margin over Cincinnati's 96-67 (.589). New York went 12-6(.667) in inter-league play, while the Reds were 7-8 (.467). So Cincinnati, at 89-59 (.601) actually enjoyed a 4.5-game, NL-only advantage over the Mets, who were 85-60 (.586) against teams in their own circuit. New York's inter-league schedule included a six-game, home-away series against the Yankees, and three games each against Baltimore, Boston, Tampa and Toronto. The Reds played a six-game, home-away series against cross-state rival Cleveland, plus three games each against Detroit, Kansas City and Minnesota --- so there were no common inter-league opponents. The Mets' IL opposition posted an overall season mark of 423-387 (.522), or 521-451 (.536) if the Yankees are double-counted. Cincinnati's inter-league opponents combined for an overall record of 293-351 (.455), or 390-416 (.484) if you count Cleveland twice. So the Reds clearly failed to capitalize on a distinct advantage in the relative strength of the two clubs' inter-league schedules.

2002 AL: Anaheim went 99-63 (.611) on the season, six games better than Boston's 93-69 (.574). The Angels were 11-7 (.611) in inter-league play, Boston at 5-13 (.278). So both clubs were 88-56 (.611) against AL-only competition. As described above, Anaheim's inter-league slate was six games against LA, three apiece versus the Reds, Brewers, Pirates and Cards. Boston played its usual six-game set with Atlanta, plus three games each against the Dodgers, Padres, Rockies and D-Backs. As noted earlier, the Angels' IL opponents posted a record of 395-414 (.488), or 487-484 (.502) if LA is double-counted. Boston's inter-league opposition came in at 430-378 (.532), or 531-437 (.549) if the Braves are counted twice. So inter-league play was the entire difference in the two teams' 2002 records, and there is no doubt that Anaheim enjoyed a huge advantage in the relative strengths of their IL schedules.

The seven division-race incidents described above represent 19.4 percent of the 36 divisional titles won in the period 1998-2003, and the two wild-card examples are 16.7 percent of the dozen WCs earned in that time. Combined, they equate to 18.8 percent of the 48 possible cases.

Obviously, I haven't had the numerous spare hours it would take to calculate the strength of schedule for the inter-league slates of every team since 1998. But in terms of inter-league schedule equity, the first three seasons of IL play (when most clubs merely competed against teams from the same division of the other league) could not have produced any truly dramatic inequities in strength of schedule. On a year-to-year basis, most divisions --- even the four-team AL West --- tend to include a relative balance of teams with winning and losing records that equates to something near a .500 mark for the division as a whole.

Based on the examples above, however, that pattern appears to have changed somewhat since the division-oriented schedule went into effect in 2001, and because --- in an effort to assure year-to-year variety in IL scheduling --- more teams are now playing inter-league slates that include clubs from at least two divisions (given the added constraints imposed by division-oriented scheduling, I assume both factors are related). As a result, it seems that larger and more frequent strength-of-schedule inequities in inter-league competition were predictable beginning with 2001, and should probably be expected to become even more frequent commensurate with additional variety in inter-league match-ups (I would also argue that the small --- and perhaps not statistically significant --- number of examples above are generally consistent with that analysis).

In that light, it seems apparent that the best way to minimize strength-of-schedule inequities in inter-league play is to utilize (much as possible) some format in which all teams in each division only play IL games against the clubs in one division of the other circuit in a season, and to avoid situations where some clubs are playing multiple teams from two or more different divisions in the other league. This could still be rotated on a yearly basis to ensure that big-draw teams like the Yankees appear in every city at least once every six seasons.

Beyond that, the simplest way to assure relative strength-of-schedule equity would be to dump inter-league play altogether. As a Sabermetrician, I find inter-league play to be something just short of a statistical nightmare, especially when trying to justify end-of-season data. As a fan, it's my subjective opinion that true competitive equity is far more important to the integrity and legitimacy of baseball as a product than the infrequent opportunity I may have under IL play to pay to see the Yankees come to Phoenix once every half-dozen years or so. Given the spread of cable television, I also believe that most fans in American League cities can see Barry Bonds being walked intentionally 12 times in a three-game set much better (and get a far clearer sense of his plus-plus skills at trotting to first base) on their televisions at home than they might from any seat most folks can afford to purchase at a ballpark.

All the same, there's no doubt that it's all about the money, and I am realistic enough to realize that as long as Bud Selig or anyone who thinks like an owner is commissioner there is no going back from where we are now. In that light, the onus is entirely on baseball management to do as much as possible to assure that competitive inequities in the context of inter-league play are minimized as much as possible. Sadly, I doubt that very many of the owners ever even give it a thought, possibly none.