Drop in Clean Sheets – Better Offence or Worse Defence?

Drop in Clean Sheets – Better Offence or Worse Defence?

“I told them, [get] the clean sheet, I buy everybody a pizza. I think they wait until I improve my offer, okay a pizza and a hot dog.” – Claudio Ranieri, Leicester Manager during their title-winning season

Clean sheets are important. For Ranieri, they are important enough to throw in a hot dog along with his already generous offer of pizzas (which he actually treated his players to) as an incentive for his players to get one. For others such as Jose Mourinho, the path to victory is always paved with the naughts that the opposition achieved during a campaign. In the last five full seasons going back to 2011-12, the eventual champions have featured in the top three teams in the clean sheet table on 4 out of 5 instances. The only time that didn’t happen was last season when Leicester got the 4th spot. Guess, Ranieri’s players were not that motivated by his pizza and hot dog offer.

cleansheets

So when last week, an avid Fantasy Premier League fan and player at work commented that the number of clean sheets has come down this season, I thought I will take a look at the numbers and perhaps be able to identify a reason for it, if it is true.

Clean Sheets Per Game Week Are Down

The number of clean sheets per game week has come down to 4.29 from 5.66 last season, or from 5.67, which is the average number of clean sheets per game week in EPL for the last five full seasons. Four teams, including the high-flying Liverpool along with Watford, Stoke City and Sunderland are yet to keep one in seven game weeks.  So yes, my friend was right in his comment that clean sheets have come down. But then the question is – why?

I could think of two reasons fewer goal keepers can keep the ball out of the goal every week this season then the last five seasons. Either, the league in general is shooting more and perhaps more on target too. With the prolific attacks that many teams in the league now possess, this is a possibility. The other reason for the dwindling clean sheets could be that goal keepers and/or defences have performed poorly, as compared to the last five seasons. I will explore both these possibilities below.

 Is the League Shooting More on Target?

A look at the data seems to answer this question in the negative. Total shots taken have improved a quite a lot to 267.71 this season, from the lowest (in last six seasons) of 257.39 last season. However, if compared against the average for the last five full seasons, shots taken has dropped just a bit (~1%) from 270.24.

Source: www,premierleague.com

Source: www,premierleague.com

Similarly, shots on target is also an improvement to 85.86 per game week this season, compared to 85.13 last season. But when compared to the average of the last five full seasons, shots on target has dropped 3.2% from 88.75.

So the total number of shots taken and shots on target are down compared to the average of last five seasons but the number of goals per game week has increased a bit (2.6%), to 28.00 from 27.27, which is the average for the last five full seasons.

Source: www.premierleague.com

Source: www.premierleague.com

Due to this, the probability of a goal being scored from a shot on target this season has increased by ~1% to 32.6% from 31.7% last season and almost by 2% from the average of last five full seasons – 30.7%. This points fingers to the defences and the goal keepers.

What’s Going Wrong with the Defences?

We find that defenders this year in general have been averse to intercepting, tackling, and clearing as the numbers for three stats are down for this year from the last year, as well as from the average of last five full seasons. But, defenders (including midfielders and forwards who drop back) can intercept, tackle and clear to ensure that a shot does not materialize. But once the shot has been taken, and it is on target, their best hope is to block it or to save it (for the goalkeeper).

After a shot on target has materialized, the only thing defenders can do is block it and because the probability of a shot on target ending at the back of the net has increased slightly, we should expect blocks to go down a bit. But, the blocks have gone up – to 74.86 per game week, from just 70.11 last season and a full 4.8% up from the average of last five full seasons – 71.42.

Source: www.premierleague.com

Source: www.premierleague.com

That brings us to the saves made by the goal keepers. These have gone up a bit from last season (57.86 vs 57.61), but compared to the average of last three full seasons (59.04, data availability issues), saves in this season have gone down by 38%. Although this is drastically inflated by the really high number for 2013-14 (61.71) but still it seems true that goal keepers are putting in less saves, not just season but over the last three seasons.

Source: www.premierleague.com

Source: www.premierleague.com

Also, this season, teams are scoring one headed goal more per game week (5.57) compared to last season (4.74) or to last five full season’s average (4.67). While the opportunities for heading could increase because of the decreased interception and tackle rate of defenders, but it could also increase because goal keepers are not being decisive and are throwing fewer punches and claiming fewer high balls.

Both of these stats are down for the current season. Goal keepers are only throwing 9 punches per game week, down drastically (25%) from 12.03 last season and an average of 11.26 (down 20%) for the last five full seasons. Similarly, goal keepers are claiming fewer high balls – 21.29 per game week this season, down 23.8% from 27.95 last season and down 27.5% from the average of last five full seasons – 29.36.

Conclusion

To me, it seems that while the number of goal scoring opportunities has not increased a lot, the probability of converting them has increased this season. While the defenders are culpable in letting some of those opportunities arise (some headed ones especially) , but the larger blame lies with goal keepers who for some reason are less active this season – they are putting in fewer saves, punches, and claiming fewer high balls, allowing more goals (especially the headed ones) to go in.

Let us see if this trend stays through the season or do some pizza + hot dog offers lure the goal keepers and defenders in the league to pull up their socks.