Friday, 7 December 2012

What the Bookmaker's Prices Told Us About Shakhtar v Juventus.

Much of the pregame chatter surrounding the Shakhtar verses Juventus UEFA Champions League tie concerned the mutually beneficial outcome should the teams draw their final group game. Shakhtar were already assured of qualification to the knockout stages, but a point would secure them top spot in the group and eliminate the possibility that they would face likely fellow table toppers, Barcelona in the first round of ties. Juventus were on much more precarious ground, a draw would also ensure that they progressed as runners up, but defeat and the highly likely win for Chelsea against Nordsjaelland would see them eliminated.

Draws are the one result that can be predicted with the least certainty. They are most likely to occur when two teams have a similar chance of winning the match outright, most usually when an inferior team, boosted by home field advantage entertains a marginally superior side. A prolonged propensity for both sides to participate in relatively low scoring matches also helps to increase the chances of a stalemate. However, even if these requirements are fulfilled the probability of deadlock rarely rises much above 30%.

Mid table teams are more likely to be involved in draws than title contenders or relegation candidates, but the discrepancy is much less extreme than it is for wins or losses. The partly random way in which draws materialise is further illustrated by the lack of season on season correlation. A team which draws extensively one season isn't guaranteed to carry this tendency onto future campaigns.

Rarely will a draw be offered at prices shorter than 2/1 or 3.0 in decimal terms, yet by mid afternoon of the Shakhtar/Juventus game the price had contracted to around 2.18, indicating a likely chance of around 45%.

Many have begun to realize the value of using bookmakers prices as a free and valuable resource. An accurate assessment of the true probability of a sporting outcome occurring is essential to any successful bookmaker, although weight of money can sometimes distort prices. We can therefore use these prices to try to piece together how this match was perceived by a combination of expert and mass market opinion.

Juventus had previously entertained Shakhtar in matchday two on October the 2nd. So early in the competition there would likely be no extraneous factors which would distort the price of the match. Prices would have reflected the relative abilities of each side along with home field advantage for the Italians. Juventus were priced up at a best price 1.61 or around 62% with the draw at 3.9 or 26% . If we use these prices from October to project a price for the rematch in December, assuming relative stability of each team's ability we would make Juventus marginal favourites once the venues where flipped and more importantly the draw would be pitched as a 27% chance.

So we had a price for the draw set at mid afternoon of the final group match at 45% when everything pointed to an expected price for a "normal" contest being in the region of 27%. The assumption across the net was that a draw was assured as it ensured a best case outcome for Shakhtar and a second best case outcome for Juve. And as that assumption gained credence, weight of money dragged the price to even higher levels of certainty. By kickoff the odds of a draw had further contracted to 10/11 or 52%.

Given the sometimes tainted history of some European club sides, were the odds telling us that the draw had been agreed or where they telling us something about the way in which the game was expected to be played out ?

The concluding matches of many competitions are atypical of what has gone before. May in the Premiership sees more goals than mid season, less cards and a collection of meaningless and meaningful matches. Stoke have faced a seemingly endless stream of late season matches where team priorities are mixed. None more so than a final game visit of Reading, already locked into a Premiership playoff position early in Pulis' initial tenure, where Stoke required a win to ensure another season of Championship football. An initially enthusiastic Reading tamely folded to a characteristic single goal defeat. In short, the Royals did what was expected of them by teams embroiled in a relegation scrap with Stoke, but ultimately they took a more relaxed stance and prepared for future matches.

A more contemporary example was seen on Wednesday night when the team selection and subsequent performance of an already qualified Manchester United saw them taste defeat at the hands of a committed Cluj, who won and narrowly failed to progress. Differing priorities, rather than collusion lead to defeats for Reading and Manchester United.

Draw prices of 45 or even 50% are virtually unheard of pregame, but they do exist in running and the goal expectancy of the Shakhtar/Juve match would decay by an amount corresponding to a 45% draw probability after around 50 minutes of initial stalemate.

The net predictably abounded with conspiracy theories regarding the match, complicated by the Russian connection between Shakhtar and Chelsea, the fall guys in any agreed draw. But more experienced opinions appeared to be quantifying the chances that the game would exist as a true contest for around 50 minutes, at which point fair play would be satisfied and the game could then be allowed to peter out to the most likely outcome under that scenario, namely a draw.

The ebb and flow of the game indicates that Juventus out shot Shakhtar by two to one until their fortuitous winner around the hour and then the hosts out shot their visitors by the same amount. So the flow of the game appeared to see Shakhtar content to protect their top slot, while their visitors attempted to claim it from them and then the host attempting to reclaim their prize once the own goal gifted it to Juve. Without the goal, the expected truce may have been forthcoming.

Fixed results are thankfully rare in football and when agreed draws do occur, the odds on offer are a lot shorter than a shade of even money, with odds of 1.2 not uncommon. What we saw initially on Wednesday was almost certainly an experienced odds maker deducing that an evenly matched pair of teams, on the night would play out a game that could become uncompetitive should it remain stalemated relatively early in the second half and even if a goal was scored, the game would contain many persuasive routes to an ultimate draw. And that opinion was reflected in the initial, mid afternoon prices for the draw, an unusual pricing for an uncommon set of circumstances.

* For anyone confused about converting the variety of different odds commonly seen to probabilities, an excellent  primer can be found here.

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