People may not be familiar with West Ham, the team currently sitting in the 8th place in Premier League table. They seem to be the typical average team that cannot compete for the European competition places but does not need to worry about relegation. The team, however, does not have a typical feature of most average team that the team does not depend on home game performance too much. The home record of West Ham this season is 7/3/3, and the away game record is 3/5/3. They received draws in their recent three games against Manchester United, South Hampton, and Tottenham Spur, two of which were in the away field. Before we talk about these three games, let us take a look at their game records against the best seven teams, 2/0/6 overall, 2/0/3 at home, and 0/0/3 away. Considering the previous bad records against top-tier teams, we can almost conclude that the team improves a lot in some parts which we will analyze later.
According to our statistic model, the opponent teams used to have a pattern on defending the West Ham offense, with 99.73% p-value; after these three games, the pattern is changed, which the opponent teams would like to use strong offense to suppress West Ham offense, with 91.49% p-value. Also, West Ham defense used to play aggressively, shoots as much as possible(99.82% p-value) to force the opponent teams to play passively (98.69% p-value). In general, the team decides to play much more passively in these three games than before.
To see the differences in detail, we also run ANOVA table in this case. We found that some performances has significant changed between games before and the last three games, such as Passing Accuracy (decreases 7.3%), number of interception (increases 4.36), number of shots blocked by goalkeeper (increases 3.17), number of shots from opponent team (increases 7.52), chances created from the opponent team (increases 4.16), and number of blocks of the opponent team (decreases 5.22). We can see from above, the opponent teams become more aggressively than usual, and West Ham literally allowed them to play aggressively.
Can we believe that the team improves permanently or temporary adjustment on strategy lifted them up in these games? We are going to use simple K-Mean Clustering to solve this question. We decide to use 4 clusters this time.
Here is the cluster assignment of each game,
And here is the game results of each clusters,
From the cluster assignment graph above, we can see a pattern, the team performance follows a pattern, transforming from cluster 3 to cluster 0 and finally to cluster 2. This would not be a coincidence. As we can see in the cluster results table, cluster 2 has the worst result among all the clusters. Let us take a look at the games in cluster 2,
Swansea 1:1 West Ham,
Liverpool 2:0 West Ham,
South Hampton 0:0 West Ham,
Tottenham Spur 2:2 West Ham,
As we can see, all these four opponent teams are either better than West Ham or at the same level as West Ham (Swansea 9, Liverpool 6, South Hampton 5, Tottenham Spur 7). When they play against the top-tier team, they tend to play passively as we stated above.
As we can see in the cluster result table above, cluster 2 has the least numbers of Shots, Passing, ChanceCreated, and Crossings, all of which are the key indicators to judge the offense. We can believe that West Ham play rather passively in all of the games assigned to cluster 2.
Do not forget that West Ham would not lift up their own performance in their home court based on our statistics model. So we can conclude that the team plays worst in cluster 2 than cluster 3, since the goal margin drops from 0.4 to -0.6. Therefore, to answer the original question, “Can we believe that the team improves permanently or temporary adjustment on strategy lifted them up in these games?” we conclude that the passive strategy temporarily lifts the team up, and this temporary success would not last long.
However, good news for West Ham, even though the team does not perform any differently in their home court, their opponent does. The opponent teams tend to shoot less (decreases 4.23), have less scoring chances (decreases 2.69), have less take on (decreases 3.15), and take more fouls (fouls increases 3.92 and cards committed increases 1) than usual. We can see that the opponent team would choose to play less aggressively when they play at West Ham home court instead of their home court. With their reputation of aggressive play in the beginning of the season, West Ham can still frighten their opponents at their home court. When West Ham chooses to play aggressively, the result is good (cluster 3 with 0.4 goal margin and cluster 1 with 1.667 goal margin). However, if they continue playing passively as what they did in the past few weeks, their opponents will not be scared of their aggressiveness anymore. When the opponent teams stop playing timidly as what they did in their home court against West Ham, West Ham will suffer from this change of pace, even though they had good results in the last few weeks.