The Liverpool Defense, we feel they deserve all caps, were a bit of a shambles last term. It started woefully enough with an own goal home to Arsenal and the misery compounded from there. 44 goals allowed. 11 losses. Playing behind that Defense was the last line of, well, defense.
Pepe Reina (above via The Telegraph) played every minute of each Liverpool league match and conceded a personal high of 44 goals (including his og in the home opener). This follows 4 seasons where he had played every match and never allowed more than the 35 in ’09-’10. Prior to that is was 27 in ’08-’09 and 28 in ’07-’08. What we want to know is if this uptick in goals allowed is the fault of Reina or the Liverpool defense as a whole.
Using Opta Sports Data we know that in 2010-11 Reina made 53 saves and faced 492 chances of which 250 were inside the box. He dealt with Liverpool making 23 defensive errors, 19 of those led to shots and 4 shots end up goals. In all, he had a very busy year. But these numbers were not far outside what could have been expected of a Premier League defense.
Initially we determined that there were 4 “tiers” of goals allowed last term:
- Chelsea 33ga; Manchester City 33ga; Manchester United 37ga
- Arsenal43ga; Fulham43ga; LFC 44ga; Everton 45ga; Tottenham 46ga; Stoke 48ga
- Bolton 56ga; S’Land 56ga; NUFC 57ga; B’ham 58ga; B’burn 59ga; Villa 59ga; Wigan 61ga
- Wolves 66ga; West Ham 70ga; WBA 71ga; and Blackpool 78ga
Goals are scored as a result of chances allowed. Therefor we can expect that for an average goalkeeper on an average team there will xgoals/chances allowed. Liverpool allowed 492 chances. They conceded a goal for every 11.18 chances they allowed. By comparison Arsenal used 4 different men in net who collaborated to provide 58 saves on 405 chances allowing 43g or a goal every 9.41 chances. The difference looks small, but consider that Arsenal’s goalkeepers would have allowed 52 goals in the same number of chance Reina faced (52.25 goals in 492 chances). That is 9 additional allowed goals over the course of the season. However, Arsenal’s goalkeeper situation was obviously less than ideal. In looking at Reina vs. The EPL Average as well as the average ‘keeper in each of the four tiers, we can see that he was on par with his peers in Tier 2. Interestingly, this info points to teams defending as a whole, including the goalkeeper.
Looking more closely, Reina fared very well when there was a defensive error. Liverpool committed 23 defensive errors, leading to 19 shots but Reina allowed only 4 goals in those situations. Of those 23 errors, Reina himself committed 4 of them, leading to 4 of the 19 shots and 0 of the 4 goals. The 4-Headed Arsenal ‘keeper saw just 16 defensive errors in front of their collected net. Of those only 9 became shots, but 7 goals were allowed. Clearly Reina was able to rescue lapses by the outfield players. And he was actually nearly twice as good as league average and was 1.25 Errors/Goal better than the next closest team (Bolton 4.5 errors/goal). By looking at these two numbers in unison it appears that the Liverpool defense let down their goal keeper.
Taking each individually – if we look only at chances allowed, Liverpool finished 4th. The Reds allowed just 492 chances. There were 10,477 chances allowed in the EPL last season. The average team allowed 523.85. But ultimately the goals allowed statistic points to the quality of these chances as much as anything.
Clearly WBA did not allow twice the chances that Chelsea allowed (441:536) but did allow more than twice the goals (33:71). Part of the answer to why is found in another set of data where it is evident that Chelsea’s defense was not as good as first assumed. Chelsea committed 24 defensive errors to West Brom’s 28, however Petr Cech allowed just 6 goals from those 24 errors. West Brom’s goalkeepers allowed 11 goals (joint 2nd worst; Tottenham) on 28 defensive errors. Liverpool certainly did Reina no favors in committing 23 defensive errors. While Reina was the best goalkeeper in the league at defending errors LFC committed them more frequently than all but 6 clubs. This difference can be directly attributed to the goalkeeper as there was not always a correlation between committing errors and final standing in goals allowed. As we noted above, Chelsea allowed just 33 goals but committed 24 defensive errors which places them among the most porous defenses. Certainly Petr Cech’s value can be better understood when realizing that Chelsea committed a similar number of errors as West Ham, WBA and Blackpool. In fact Chelsea was well below average: the average team allowed just 18.65.
In this exercise there are myriad variables we can not account for. We have no way of knowing how much the defender put off the shooter, to what degree the goalkeepers reputation forced the shooter to try for a more narrow window of opportunity than they would have against a lesser foe, if the ball was wet or properly inflated. All of those factors could contribute to a chance being missed without forcing a save. Since we’re unable to account for them, we have to presume that any tangible factor shows up in the data, and acknowledge that if it is not tangibly accounted for with the data we’re using, we’re ignoring it at present. Based only on last year’s data, Pepe Reina may have played slightly below his own expectation, but he played better than the Liverpool defense as a whole. Reds fans will be hoping that the Kenny Daglish can reform the teams defensive approach and reap the benefit of having Reina at the back.