Just look at the change in the odds of the game Liverpool-West Ham, scheduled for next Saturday, after Steven Gerrard was injured in yesterday’s friendly match between England and France.

Betting odds for a Liverpool win against West Ham [Captured in Greek version of Betfair.com]

The odds for Liverpool are currently at the highest level so far, recording one of the biggest changes in football betting today, when they climbed to 1.60 from 1.40 set originally. The market seems to want to reflect the news on the odds, as always happens with the news or even rumors circulating the media.  Similarly to what happens in the stock market, price behavior proves to be a very honest indicator.

Having already discussed about the influence of rumors and news when betting the odds, unexpectedly this week we find the best example of how players’ injuries and last-minute changes to line-ups’ affect the betting odds of football games.

In principle, a football system, which is based on mathematics and statistics, provides forecasts depending on statistical data for each team. Parameters such as the average number of goals, league ranking and previous performance are usually the factors that a bettor would include in a football betting system.

Still, there is always difficulty in integrating news like injuries and lineups, as statistical values into our system. For example, how could a bettor evaluate Gerrard missing the game today, which clearly affects the ability of Liverpool to win the game, while at the same time betting odds have already been changed?

A solution to this problem could be to give points to teams if all players are available for the match.  When a football team starts the match with all key players in its lineup, we mark the team with 20, for example.  If the main striker or the main goalkeeper won’t show up, we reduce the value to 16. If an average player is not available for the match, we decrease our evaluation by 2 points, while in the case of a player who is not very important for the match, we subtract 1 point.

That sounds like an easy plan.

In this way we classify the teams according to the importance of injuries and final lineup, despite the rough method.  Nevertheless, we are able to take into account the parameter of missing players and injuries in the football system that we are trying to build.

If Liverpool had no problems with Gerrard, as West Ham has no players missing the game, we would say that the system treated both teams with the same coefficient 20, in terms of lineups. By changing this parameter against Liverpool, the system should recalculate the chance of a tie, increase the prediction in favor of West Ham and reduce the chance of Liverpool winning the match.

So the input of this parameter in the final equation for calculating our forecasts, naturally will predict a lower chance for a home win.  If the system previously indicated a value bet at 1.30, now a value bet should rise to 1.50 or higher, since the probability in favor of Liverpool is reduced.

However, since the odds have already surpassed the 1.60 level, we must not bet just because of the injury of Gerrard.

Note that values in our example are randomly used in order to better understand the importance of absences in a sports betting system.