At average odds of 50.7% would estimate the win inflation at almost half a win per team in the NL, bringing the vig on NL Win Percentages close to only one percent. If other books start offering lines on this, you can almost certainly get to positive expected value with a little line shopping. Even if this is the only book that has this offering, it would be a good place to focus your handicapping efforts as this is a pretty good market, all things considered.
Caveats and Extensions
Certainly, this analysis relies on a variety of assumptions. One of those assumptions is that interleague games are removed. If interleague games aren’t removed, betting the NL Unders is probably no better than betting the AL Unders.
Second, we make the assumption that only 20 games are removed from each schedule per team. Should fewer games be played, we would expect the push probability for win totals to increase, but we’d also expect more variance in final win probabilities. It’s hard to tell the net effect of fewer games.
Third, if this wager type is maintained once the total number of games is determined, it might behoove you to pay close attention to exact win percentages for a particular number of wins. For example, if the season is 110 games and a team wins 56 games, their win percentage is 50.9%. If you bet under 50.5%, you’re a loser. But if you bet under 51.0%, you’re a winner. That extra 0.5% between 50.5% and 51.0% is significant. On the other hand, if that team wins 57 games (one additional game), their win percentage is 51.8%. 51.0%and 51.5% are both losers. Thus, there is no difference between 51.0% and 51.5%if there are 110 games. Just something to keep in mind.
Last thought – this same thought process can be applied to the analysis of win percentages for particular divisions. The AL Central, for example, is particularly weak this season. Their average posted win percentage on DraftKings is 47.8%. If for some reason, the schedule is changed to have a much higher percentage of divisional games, there may be some value on the Win Percentage Over for AL Central teams.
If you’re betting these markets, I hope this helps you build a strategy to squeeze out as much value as possible.