Tuesday, 14 May 2013

Game States And Team Quality.

In my previous post I looked at how Arsenal's attacking and shooting tendency was tailored towards the particular game and scoreline states in which they found themselves over the 2010/11 season. Arsenal were the pregame favoured team in virtually all of their 38 Premiership matches in that season and it was only in the four matches where they traveled to Liverpool, Chelsea and the two Manchester sides that they went into the contest as underdogs. Consequently, the scoreline state and game states mirrored each other fairly well. A lead was obviously a good game state, a draw could almost always be improved upon compared to pregame expectations and when trailing, the Gunners had both the incentive and almost always the potential ability to turn the scoreboard around.

However, in the case of more mediocre sides, these correlations aren't always as clear cut, especially when the game is stalemated.

The final 2010/11 table was a fairly typical example of the recent Premiership. Manchester United were comfortably crowned champions, Chelsea, Arsenal and Manchester City followed them home in a tight group of three and then came those aspiring to qualify for the Europa league. The mediocre EPL sides then begin to appear and going into the final round of matches just seven points separated 9th place from 19th. Therefore, Aston Villa, 13th after 37 games and 9th a game later could reasonable be chosen as a typically, run of the mill side.

Villa were the favoured side in just 17 of their 38 games and unlike Arsenal, there would likely have been many more games where a draw would have been an acceptable result for the team from the West Midlands. So where Arsenal's approach would be consistently to tend towards pushing for a go ahead goal, the connection between Villa's scoreline state and game state is likely to be more ambiguous. A current point away to Fulham was most probably acceptable, (although they may harbour thoughts of capturing all three), but one at home to ultimately relegated Blackpool would be much less acceptable. In short, the scoreline states don't coincide as neatly with a side's perceived game state in the case of Villa compared to Arsenal.

Similarly when Villa trailed, their ability to match the desire to improve the scoreline with their capability of achieving that aim is also unlikely to tally with that of Arsenal. Villa trailed at some stage on 19 occasions, against teams who were as determined to hang onto their three points as Villa were to retrieve something from the match. So the change in scoring effort from Villa is likely to be a function of these shifting priorities shown by each side. When the same thing happened on 14 occasions to Arsenal, the Gunners had a more potent attacking force to call on for a more concerted retrieval approach than did the Villans in their various contests.

As with the previous Arsenal analysis, I've used the x, y data of the shot to determine a goal expectation, which in turn leads to an expected long term scoring rate in different scoreline states. At worst, this type of analysis can give an enhanced picture of how Villa tried to play during different phases of matches in that season and we may also be begin to see the interaction between teams without painstakingly plotting minute by minute changes in game state.

Aston Villa's Goal Expectancy From Chances Created in Various Scoreline States.2010/11.

Scoreline State. Ahead. Level. Behind.
Goal Expectation From Chances Created. A Goal Every 72 Minutes. A Goal Every 52 Minutes. A Goal Every 58 Minutes.

We see a similar trend to that exhibited by Arsenal. Chance creation and long term scoring rates decline when Villa led, compared to other scorelines. Shots were less frequent and marginally of the lowest quality on average. Interestingly, potential scoring rates are actually highest when games were level, Villa were creating best and most frequent chances in this scoreline state. Numerically, creation rates only fell away very slightly when they trailed, but quality was noticeably poorer.

All Hands On Defence As Villa Protect A Lead.
These changing rates coupled with those produced by Arsenal in the same season, hint at the changing dynamics of a football game, where desire and capability are pitched against opponent ability and intent. The game state at level scorelines is likely to be less clear cut in the case of Villa compared to Arsenal. In the former, both sides may be still be actively seeking a win, whereas the opponents facing Arsenal are likely to be more uniformly engaged in defending their point. In short, when drawing Villa are more likely facing teams who are also willing to take a chance.

Once Villa trail the eventual priorities are more clear, but as Villa lack the attacking expertise of the top sides, exemplified by Arsenal, their ability to create valuable chances may now be less than they were capable of achieving in a more open situation where both sides may still have been trying to break a stalemate.

Overall the Villa figures show a similar general trend as Arsenal in 2010/11. Both sides were at their least dangerous in goal scoring terms when already ahead. The differing potency of both Arsenal and Villa at level or trailing scoreline states may merely be simply an artifact of sample size or it may represent a genuine difference between the very best in such situations and the mediocre.

Often in football analysis, such as the relevance of possession, the characteristics of the very best overwhelm the tendencies of the less gifted majority, in turn hiding a more complex reality and this may be the case in determining game states for different teams under the same scoreline, especially stalemates.

Ultimately, game states will have to be defined by the non trivial interplay of relative team quality, current scoreline and time remaining.

No comments:

Post a Comment