If we take a look back at the 2012/13 PL season we always find cool little nuggets of information that may help us, at least a little, to understand the 2013/14 season which is currently unfolding.
Save% tends to regress pretty heavily back toward the mean to the tune of ~69% from one season to the next. Grayson's actual save% numbers are a little different here due to a different data source but the regression number should be in the ballpark.
Save % average is ~70% but some good teams, or especially bad teams may well have an average north or south of that 70% number. Score effects is one possible reason for sustain in a high/low save%. Some kind of magic voodoo in shot quality caused by unique systems or talent disparity may well be another.
Anyhow, I plotted all 20 team save% numbers from 2012/13 and turned those numbers into rolling averages. I was aiming to make some pretty graphs and I wanted to search for a couple of things:
- Did any team(s) manage to sustain crazy high save percentages throughout the season.
- Did any team(s) manage to suffer through consistently low save percentages.
- We're there any examples of spectacularly fun drop-off-a-cliff regressions of save percentage.
- Teams of Interest: Man City, United, Arsenal's absurd charge for 4th pace etc etc.
Stoke had a really high save % for the first half of the season: ~75% at the 9 game mark; 81% at the game 19 mark. Stoke's first half season of save% could well be systems - it sure looked like systems at that point - and then in the second half of the season this happened to Stoke's save%:
Liverpool's first half of the season was average in terms of points gained and Liverpool's save% was definitely a part of that. Liverpool posted strong results in the second half of the season backed by a rapidly improving save%.
High Save% Teams
Swansea and Chelsea are the two teams how most clearly exhibited consistently high save percentages in 12/13. Systems? Probably. Personnel? Probable in both cases. The reasons for those excellent save percentages remain a little unclear, and although there was some slight regression in both teams' save percentages there was far more sustain.
Low Save% Teams
We know that Wigan have posted some poor save% numbers in previous seasons and 12/13 was no different. The most obvious cause is Wigan's low save% may well be the lack of talent that the club could field. Wigan, consistently the most over matched non-yo-yo squad in the last 5 years, just could field good enough defensive personnel.
Southampton posted a dreadful save% but the causes to that save% are less clear. Southampton changed managers mid-season and thus changed systems. Southampton, if memory serves weren't the most talented squad in 12/13 but by no means the worst. It's a very low save% considering the plaudits Pochettino has earned for his defensive scheme in 13/14.
In 13/14 Southampton and Pochettino were lauded around the 7 or 8 game mark for their defensive play. Save%, among other things, was held up as evidence of such tight defensive schemes. Fair enough. Then this happened:
I'm confused by Southampton save%. Pochettino may well be able to coach a strong defensive scheme but he is still at mercy to the will of the save% gods. Or, maybe, just maybe, Southampton's first 8 games of the 13/14 season were simply a 'hot spell' of save% and not indicative of any sustainable trend when placed against Pochettino's full sample of Save%.
Pochettino's full Save% sample is a shade under 70%, which is just about league average.
Teams Of Interest
Arsenal are slightly above average but, importantly, they improved during that historic run for 4th place. Man City posted an erratic save%, and Tottenham posted a consistently below average save% which probably didn't help their failed bid for 4th place.
The last thing to note is the spread of save% between the best team(s) and the worst team(s). Just look across the graph above and pick, say, 6 game intervals and look at how the spread between the best save% teams and the worst save% teams decreases as games played increases. Regression.
The regression of the high save%'s and the low save%'s in 13/14 probably tell us some things about what may happen to Arsenal's high save% and Sunderland's low save%.