Oct 8, 2015
Oct 8, 2015

Betting on the NBA preseason

Betting on the NBA preseason
The NBA is the latest of the North American sports to kick-start their campaign, when the preseason gets underway on 2nd October. With teams experimenting and honing their tactics, can bettors take advantage of this? Mark Taylor examines the options.

The warm-up to the regular season lasts three weeks and teams will play up to eight matches at a variety of venues, occasionally against non-NBA international guest teams, before the regular season begins on October 27th.

The purpose of preseason

As is also the case in the NFL and Premier League soccer, wins in the NBA preseason are not always the main priority for teams.

A new line-up, either comprised of acknowledged superstars, hopeful rookies or journeymen veterans and newly appointed coaches mean different tactical approaches are often honed and experimented with, sometimes at the expense of match outcomes.

In a sport with a large number of scoring events where only five players per side are on the court at any single time, the influence of one outstanding player can have a disproportionate effect on the result, but their playing time will often be limited compared to the regular season.

Therefore, the coach’s intentions and likely player rotation, often revealed on local news sites, are an additional distraction when betting in the preseason.

A seasoned veteran may have little upside compared to an exciting rookie, but the former may be a more reliable contributor at present, while the new prospect often faces a steep learning curve in the professional game.

So, while it may be relatively straightforward to discern which teams are likely to retain the majority of their ability, be it good or bad, from previous seasons and those who are embarking upon a rebuilding phase or have acquired an acknowledged superstar, the preseason remains an area where uncertainty and speculation weighs heavy on the spreads and money line quotes.

Using Pythagorean expectation followed by a venue specific application of Bill James’ Log 5 method to the scoring and conceding record of teams presents a consistent framework with which to frame baseline match odds between teams.

Spotting value on the spreads and money lines

The preseason potentially offers an advantage to those prepared to follow the up-to-date news coming out of the NBA camps, although it should be no surprise to learn that the lines set by the bookmakers are still highly correlated to actual preseason results.

Over the preseason since 2009/10, omitting the lockout shortened 2011/12 campaign, the general match odds posted in the preseason have been very good indicators of the actual game outcome.

For example, 120 home teams were relatively strong favourites in the preseason with implied win probabilities including the bookmaker’s margin ranging from 0.6 to 0.65. They had an average winning probability of 0.62 and were successful over 60% of the time.

Similarly close relationships have existed for different strengths of home favouritism over the previous five complete preseasons, although individual years do inevitably produce subsets that may appear profitable to follow, they rarely persist into subsequent years.

Using Pythagorean expectation followed by a venue specific application of Bill James’ Log 5 method to the scoring and conceding record of teams presents a consistent framework with which to frame baseline match odds between teams.

However, such approaches are ignorant of team rotation, the intentions of a coach and whether the game is a preseason or regular season affair.

Case Study: San Antonio Spurs vs Atlanta Hawks

The exponent for basketball is 13.91 to reflect the greater scoring in the sport. Therefore a side, such as the San Antonio Spurs, who scored 8639 and allowed 8006 points in 2013/14, would have a Pythagorean expectation of (8639^14)/(8639^14+8006^14) = 0.74

This compares to the actual winning percentage of 0.76 from their 62 wins during the regular season.

The Atlanta Hawks won 34 games in 2013/14, scoring 8282 points to 8321, giving the team a Pythagorean Expectation of 0.48.

So in a regular season contest, San Antonio would expect to be favoured strongly if they played host to the Hawks.

By applying James’ Log 5 method to such a match up, we get the chance of a Spurs’ home win as follows:

Home Win Probability = (0.74*(1-0.48)*(0.6))/ ((0.74)*(1-0.48)*(0.6) + (1-0.74)*(0.48)*(1-0.6)), where 0.6 is the winning percentage for home teams.

This comes to an expected home winning probability for the Spurs of 0.82.

If we calculate match odds for the preseason using the Pythagorean and Log 5 method from the previous regular season for all sides, as in the case of the bookmaker’s quoted odds, there is a relationship between Log 5 odds and actual outcomes, but with one important proviso.

Longer priced, preseason home underdogs win more often than the Log 5 generated odds suggest should be the case, while short priced home favourites, such as the Spurs were against the Hawks, remain favoured, but not as strongly.

A variety of factors such as squad rotation and experimentation, make games, which could be regular season mismatches, more closely contested in the less intense preseason.

For example, in the previous five years of complete preseasons, 99 home teams have had a log 5 match winning expectancy of 0.4 or lower, based on theirs and their opponents previous regular season scoring data, averaging a winning expectancy of 0.3. However, in reality, over 40% of these matches have actually ended in home wins.

Similarly, 67 home sides have had a Log 5 win probability in excess of the 0.82 projected for the Spurs against the Hawks in the 2014/15 preseason, and just 63% won.

Preseason conclusion

In short, a variety of factors such as squad rotation and experimentation, make games, which could be regular season mismatches, more closely contested in the less intense preseason.

These additional factors appear to be incorporated into bookmaker’s posted odds, but not in a simple Pythagorean derived estimate using last season’s data.

So, while standard analytical tools can be used as a factor to solve the preseason puzzle, winning is not as high on the agenda as it is in the regular season and the numbers, while still a helpful guide to which side might be favoured, should not be taken entirely at face value.

With the preseason in full swing, there is a chance for bettors to put their findings into practice, Pinnacle offer the best NBA betting odds and highest limits online.

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