Performance analysis of sport allows the collection of accurate and objective data in relation to performance. This data can be used to relay feedback to athletes or coaches in order to further develop strengths or improve weakness. Identifying the key performance indicators that discriminate between successful and unsuccessful teams may allow coaches to make inferences on strategies and tactics to ensure successful future performance. With the huge financial gains that elite level football clubs stand to make from competing successfully in their respected competitions, the coaches search for success or means to improving performance becomes extremely important. The financial rewards to successful clubs is reflected in the English Premier League where in the 2013/2014 season, teams were awarded an extra £1.2 million per finishing place (£22.3 million difference from top to bottom).
The most common method of collecting data on performance is through the use of digital cameras and computerised notation. Early methods included hand notation systems, which although were accurate, could be very time consuming when processing the collected data; hand notation systems may also require considerable learning time to become familiar with. Performance analysis can provide information on several areas that include physical, tactical and technical. This literature review will look a sample of current literature available in relation to tactical and technical aspects of the game and how the identification of key performance indicators such as possession of the ball, shots at goal and passes may differ between successful and unsuccessful teams. All reviewed studies are inclusive of elite level domestic competitions rather than international tournaments to attempt to give a more accurate picture on overall team performance; successful from unsuccessful teams are defined by current or final league finishing positions. Ultimately the deciding factor in determining whether a team is successful or not is the final score of a match and ensuring that the number of opportunities that are consequently converted to goals, outnumbers the opponents. Interest is then in how these opportunities are manifested.
For example Rees, James, Hughes, Taylor and Vuckovic (2010) found that successful teams were able to create more attempts at goal through a particular area of the field in the attacking third named ‘zone 14’, directly in front of the opponents eighteen yard box. Their method of analysis consisted of splitting the pitch into eighteen equal sized zones in order to describe fully the activities of match play (Fig1).
Fig 1 showing football pitch with 18 zones of equal size.
The investigation found that successful teams converted significantly more possessions from zone 14 into shots at goal, with the more successful teams converting more chances, indicating a preference of quality over quantity; more goals were converted from zone 14 than in wide areas (10 vs 5) but due to the small sample size of twelve games from teams in the English Championship (the second tier of English football) there are limitations to this data. The study shows the importance of quality of possession in zone 14 over the frequency. This can aid coaches to instill a more passing style of play rather than a direct method, emphasising patient build up play to enter zone 14 in order to create attempts at goal.
In a similar vein Lago-Penas and Dellal (2010) highlighted that more successful teams maintained a higher amount of ball possession and more stable patterns of play than unsuccessful teams. From the three hundred and eighty matches analysed from the Spanish top division retention of possession was strongly related to successful performance. For example, the top finishing team Barcelona recorded a mean possession of 65.29% compared to bottom team Recritivo, who averaged 48.05%. But, ultimately possession strategies were found to be influenced by situational variables, such as match status, match location and quality of opposition. Interestingly possession was always found to be higher when losing rather than winning, indicating a change in tactics from the losing team in an attempt to try and control the game in order to create chances. Away teams reduced possession by 2.43%, which could be down to unfamiliarity of stadium, or the advantage from the home support. In contrast to this the top team showed a lower coefficient of variation (Barcelona CV 8.42%) compared to the bottom team (Recritivo CV 17.1%) eluding to the fact that the better the quality of the team, the less situational variables are relevant. This may imply the importance for coaches to instill a fluidity to their teams, with the ability to alter strategies and tactics efficiently and effectively, particularilaly in relation to match status. In contrast to this Huges and Franks (2004) found that the conversion ratio of shots to goals was higher from direct play rather than possession; but interestingly also found that there were significantly more shots per possession after longer passing sequences. This study stated that successful teams should use short passing sequences (direct play) given the better conversion ratio of shots to goals, but variables such as quality of opponent were not taken into consideration. An opponent of higher technical skill may have that ability to play a high possession strategy and still be able to be successfully convert attempts. The role of the coach here would be to assess the ability of the team in order to employ the most effective strategy.
The same situational variables were used by Almeida, Ferreira and Volossovitch (2014) in a study into regaining possession of the ball. A sample of twenty eight matches from the UEFA Champions League looked at the situational variables on ball recovery type (interception, tackle, set play, turnover, goalkeeper rebound) and zone. As all teams had achieved a certain level of success in their domestic league, which qualified them to compete at the preeminent level of European football, all of a paramount standard. Overall, interceptions were shown to be the most frequent ball recovery type (36.9%), with most possessions regained in the defensive zones (81%). Match location had the most significant effect on ball recovery, with home teams having increased odds of 134.2% compared to visiting teams in regaining possession in offensive areas; but interestingly the more successful teams (teams that proceeded further the tournament) showed the ability to regain possession in more advanced areas of the pitch by employing more proactive defensive strategies in pressurising the opponents higher up the pitch and forcing opponents to play with no intention to keep possession or to make errors. This may be significant in coaching the improvement of player anticipation of passes in order to look for interceptions, and also a playing style that can be adopted, of defending away from own goal and in more advanced positions. In order to this there must be unity within the team and a clear understanding of player roles set out by the coach.
Lago-Penas, Lago-Ballesteros, Dellal and Gomez (2010) attempted to identify the critical instances that discriminated winning, losing and drawing teams in the Spanish Football League concluding that total shots, shots on goal, crosses, crosses against, ball possession and venue were all critical variables in differentiating between successful and unsuccessful teams. This study again points to the importance of converting possession into successful attempts at goal.
Situational variables appear to play a key role in the final outcome of a game, more so location, with home teams exhibiting a clear advantage over away sides. This is likely to be down to the familiarity of environment to home players and also increased home support. In order to score a goal in football, a team must be in possession of the ball; from the selected research the methods teams employ when in possession of the ball vary according to playing style and technical ability of the team. A team that are able to utilize both a direct style of play and possession play in response to evolving match score would appear to be more successful.