A Look Back at Interleague Play

Now that all of the Interleague games are over for this baseball season (except of course for the All Star Game and World Series and the one rain-out to be made up in September) I want to recap the results for you a little bit. I will also give a quick recap of the NHL season and the NBA Finals (sorry for the delay).

Traditionally, we have seen betting action taper off a little bit during Interleague play, but this year the decline was less than in past seasons. I think bettors are getting used to betting on these games and there is also more data available now that this change in format has had a few years under its belt. For example, we have seen the Yankees and Mets play before and we now have some basis for comparing lines and results when they play now. (See Frontlines Issue18 – The Effects of Interleague Play for more on the effects of Interleague play). In previous years the drop off has been as much as 30%, but this year there was a less than 15% drop from what we saw the rest of the month on a per-game average. When you consider that many of the regular games this month benefited from a less-than-full schedule (fewer games means higher per-game betting for books) then the drop, because bettors are wary, is probably far less than 10%.

Interleague play has also traditionally been good for books because the same uncertainty that keeps some bettors away seems to result in more balanced action and so books can make a similar profit with less risk. Plus, there seems to be more upsets than normal. For example this year, who would have predicted the NL-cellar-dwelling San Diego Rondell Whites!er Padres!would take four of six from the AL-leading Seattle Mariners? In past years we have seen as much as a double in the bottom line hold percentage for Interleague games over regular games. We did see an increase over the rest of the season this year but it was not as large as in previous seasons. It seemed like there were fewer upsets this year and in fact, the good teams seemed to continue to do well. I compared win percentages from the Interleague games for all the teams with win percentages from regular league games and the linear correlation was 64%. (For those that didn’t take stats in college, this means that a team’s regular win % would be a pretty good indicator of how it would do in Interleague play). Every team’s Interleague win percentage was within 22.2% of their win percentage for regular league play and half the team’s were within 10%. Most improved were the aforementioned Padres (Interleague was .444, up from .308 the rest of the way), Anaheim (.611 from .468) and red-hot Arizona (.714 from .522). The biggest disappointments were three teams from the AL basement: Tampa Bay (Interleague was a MLB-low .167, even worse than their .371 league play), Baltimore (.278 down from .484) and Texas (.222 down from .444). The Yankees had the best Interleague record at 13-5 but that shouldn’t really count as they got to play the Mets 6 times.

Here are a few stats/trends from this season’s play: NL was 136-114 (.544) up from 129-122 (.514) last season Home teams were 135-115 (.540) up from 130-121 (.518) AL at home was 63-62 (.504), the exact same record as last year NL at home was 72-53 (.576), a jump from 67-59 (.532) Home teams were 50-34 (.595) in the first game of each series but just 85-81 (.512) in the other games.

For comparison, home teams are .534 for all of 2003 (.515 in the AL and .550 in the NL) so it appears that NL teams did a little better at home in Interleague play than expected and AL teams did a little worse. I said in my column on Interleague play last year that it seems that the quality of team may be more important than home-field advantage. I stand by that this year and let me add that oddsmakers know bettors will overcompensate for home field advantage. Just something to think about come next June.

Speaking of June, another very long hockey season has come to an end. Overall it was a very good hockey season for us but the last few weeks were a little tough. Handle was up over 120% year-over-year and that makes hockey one of our fastest growing sports even though it is still just a fraction compared to NFL or NBA. The playoffs got off to a great start with big wins for the House on Anaheim’s upsets of Detroit and Dallas (there were a few bettors that bet the Red Wings and doubled up after each loss so the sweep was very costly for them) but bettors had some revenge down the stretch and they did very well in the Finals as most backed the Devils. The most costly thing for us was a couple of large bets on the Devils to win the Stanley Cup and Anaheim to win the Western Conference placed months ago. Usually Futures are very good for books as the theoretical win percentages are very large, but not on this occasion. My feeling is that if you picked the Ducks to win the West back in January, then you deserved the big payoff!

We also had a couple of players do very well in picking the Spurs to win it all months ago (they were my pick in December but mostly because I am a Navy brat and thus a big David Robinson fan), but there was also a lot of money on the Lakers, Mavs and Kings so we did OK on NBA Futures. I talked about the basketball season in depth in my last column so let me just sum up the Finals quickly. For the pointspread, money was pretty balanced for the first 2 games but San Antonio got heavy action on the road in Games 3 and 5 so those were big losses for us. However, we did very well in Game 6 when bettors loaded up on the Nets (the trend of the public liking the road team definitely continued). Bettors had a tough time with the totals though. The public typically likes the Over but played the Under in Game 1, the only game to go Over the number. The public was on the Over the rest of the way but the last 5 games all went Under so the book was a perfect 6-0 on totals. Overall, the 2 big losses were evened out by the wins on the totals and Game 6. We did well on moneylines and were happy to have made a profit on the Finals after having a very tough June last year in the NBA.

Football season is just around the corner so I will be writing more regularly again. I’ll be back in a couple of weeks with some more baseball analysis that I promised a couple of months ago.

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