The Importance of Defence in Winning Promotion to the Premier League

Executive Summary

  • In the 2015/16 Championship goals conceded were a much stronger predictor of league performance than goals scored.
  • The strongest teams defensively all finished in the top six.
  • Despite their attacking strength the promotion hopes of both Fulham and Brentford were fatally undermined by defensive weaknesses.
  • Keeping a clean sheet has a league points value more than double that of scoring a single goal.
  • Defensive efficiency (based on the ratio of opposition shots on target inside the penalty box relative to total defensive contributions) is a very strong predictor of goals conceded.
  • Improved defence is a cost-effective Moneyball strategy for improving league performance based on tactical organisation, coaching and practice.

 

It’s very early days in the Championship and a mug’s game to predict with any certainty who will be promoted with so few games played. But already there are ominous signs for the promotion prospects of Nottingham Forest, Burton Albion and Blackburn Rovers. Why? Quite simply they have been defensively weak in their first four games and a strong defence is a fundamental building block for any team with serious ambitions of getting promoted to the Premier League.

 

So what’s the evidence to support the assertion that defence is crucial to winning promotion to the Premier League? Well let’s look at the final league table for the Championship last season.

 

Final League Table, FL Championship, 2015/16,

  P W D L F A Pts
Burnley 46 26 15 5 72 35 93
Middlesbrough 46 26 11 9 63 31 89
Brighton & Hove Albion 46 24 17 5 72 42 89
Hull City 46 24 11 11 69 35 83
Derby County 46 21 15 10 66 43 78
Sheffield Wednesday 46 19 17 10 66 45 74
Ipswich Town 46 18 15 13 53 51 69
Cardiff City 46 17 17 12 56 51 68
Brentford 46 19 8 19 72 67 65
Birmingham City 46 16 15 15 53 49 63
Preston North End 46 15 17 14 45 45 62
Queens Park Rangers 46 14 18 14 54 54 60
Leeds United 46 14 17 15 50 58 59
Wolverhampton Wanderers 46 14 16 16 53 58 58
Blackburn Rovers 46 13 16 17 46 46 55
Nottingham Forest 46 13 16 17 43 47 55
Reading 46 13 13 20 52 59 52
Bristol City 46 13 13 20 54 71 52
Huddersfield Town 46 13 12 21 59 70 51
Fulham 46 12 15 19 66 79 51
Rotherham United 46 13 10 23 53 71 49
Charlton Athletic 46 9 13 24 40 80 40
MK Dons 46 9 12 25 39 69 39
Bolton Wanderers 46 5 15 26 41 81 30

 

A casual inspection of the league table suggests that goals conceded rather than goals scored are a better predictor of league performance, and this is indeed the case. Simple regression analysis indicates that goals conceded alone explains 74.4% of the variation in league points whereas goals scored only explains 60.2%. The clubs finishing in the top six all ranked as the best defensively and the three clubs winning promotion to the Premier League – Burnley, Middlesbrough and Hull City (via the play-offs) – had the three best defensive records in the Championship, averaging only 0.73 goals conceded per game which represents a 39.6% performance gain compared to the league average of 1.21 goals conceded per game. By comparison the three promoted clubs had a 23.9% performance gain in attack, averaging 1.50 goals scored per game. Middlesbrough in particular provide a very compelling case for the relative importance of defence over attack, having the best defensive record in the Championship last season but ranking only 8th in goals scored, and winning automatic promotion on goal difference over Brighton and Hove Albion due crucially to conceding 11 fewer goals.

 

Brentford and Fulham both demonstrated last season how a weak defence can seriously undermine a promotion push. Both clubs out-scored Middlesbrough and indeed Brentford were joint top scorers with Burnley and Brighton and Hove Albion. But Brentford could only finish 9th after averaging 1.46 goals conceded per game, the 8th worst defensive performance in the Championship and only marginally better than MK Dons who were relegated. Fulham performed even worse defensively, having the 3rd worst defensive record after the two relegated clubs, Bolton Wanderers and Charlton Athletic.

 

The importance of defence is often undervalued as Anderson and Sally persuasively argue in The Numbers Game (Viking, London, 2013). It’s partly a form of decision bias because attacking success (i.e. goals scored) is a positive observable event whereas defensive success is all about non-occurrences, not allowing the opposition to have shots at goal and not conceding goals. We tend to over-emphasise positive observables and undervalue non-occurrences. Anderson and Sally call it the ‘inequality central to understanding football’. In football 0 > 1 because ‘goals that don’t happen are more valuable than those that do’. (p. 131). The expected value in terms of league points from keeping a clean sheet in a game is considerably higher than the expected league points from scoring a single goal. Anderson and Sally analysed the points value of goals scored and conceded in the Premier League over 10 seasons and found that a clean sheet had an expected points value of nearly 2.5 whereas scoring a single goal had an expected points value of only just over 1.0. A very similar pattern is observed in the Championship last season.

 

Points Value of Goals Scored and Conceded, FL Championship, 2015/16

Blog 6 Graphic.png

 

Keeping a clean sheet yielded an expected return of 2.3 league points in the Championship last season whereas scoring a single goal yielded an expected return of 1.1 league points. The three promoted clubs had the most clean sheets with Middlesbrough amassing 22 clean sheets while Burnley and Hull City both had 20 clean sheets. In contrast, Fulham had only 4 clean sheets and Brentford had only 8 clean sheets, the same number as the bottom club, Bolton Wanderers.

 

Defence is an obvious Moneyball strategy in the sense that developing an effective defence tends to be a more cost-effective way of improving performance. The football players’ labour market tends to reflect the decision bias towards goals scored with strikers attracting a substantial salary and transfer-fee premium. Defenders have tended to be undervalued although perhaps at the top end the recent transfer of the young defender, John Stones, from Everton to Manchester City, may signal a market correction. But an effective defence is also cost-effective because ultimately it is down to tactical organisation especially good positional decision-making that can be improved through coaching and time on the training pitch. Defending is reactive and in some ways much more amenable to coaching and practice than attacking which is more creative and instinctive and hence much more difficult to coach.

 

Effective defending is partly about effort but as always it is not just the quantity of defensive activity but also the quality of that defensive activity. Defensive effort as measured by the total number of challenges, blocks, interceptions and clearances partly reflects possession share with struggling teams having to defend more. In addition good defending is as much about being in the right place at the right time and so isn’t necessarily reflected in tally counts of actual defensive contributions – what Anderson and Sally call the “Maldini Principle” or “dogs that don’t bark”. I have found that a useful measure of effective defence is the ratio of opposition shots on target inside the box (measured as the deviation from the league average) relative to defensive effort. I call this ratio “defensive efficiency” (and scale it by 104 for presentational purposes) since it measures defensive output (shots allowed) relative to input (defensive effort). Good defence is about restricting the number of opposition shots at goal but not all shots at goal are of equal threat as expected goals analysis has highlighted. The most dangerous shots are those from inside the penalty box on target and so restricting this type of shot is the critical aspect of effective defence.

 

Defensive Performance, FL Championship, 2015/16, Ranked by Defensive Efficiency

  Defensive Effort Opposition Shots Opposition Shots On Target Inside Box Defensive Efficiency Goals Conceded
Derby County 94.674 11.891 1.935 89.17 43
Hull City 96.065 10.587 1.957 85.62 35
Middlesbrough 99.804 11.370 2.109 67.16 31
Blackburn Rovers 93.304 11.652 2.348 46.21 46
Sheffield Wednesday 92.065 11.000 2.370 44.47 45
Burnley 96.043 14.391 2.370 42.63 35
Brighton and Hove Albion 92.761 11.804 2.413 39.45 42
Preston North End 95.543 11.957 2.435 36.03 45
Wolverhampton Wanderers 104.739 13.500 2.435 32.86 58
Queens Park Rangers 103.043 12.261 2.609 16.53 54
Reading 96.826 10.783 2.739 4.12 59
Ipswich Town 93.957 13.348 2.761 1.93 51
Nottingham Forest 110.674 14.043 2.826 -4.26 47
Huddersfield Town 95.304 11.065 2.848 -7.22 70
Cardiff City 96.565 12.717 2.870 -9.38 51
Bristol City 91.826 12.783 2.957 -19.33 71
Birmingham City 98.761 14.109 3.087 -31.18 49
Leeds United 93.891 12.783 3.087 -32.80 58
Brentford 92.239 12.978 3.196 -45.17 67
Charlton Athletic 100.348 16.587 3.283 -50.19 80
Bolton Wanderers 100.609 14.435 3.413 -63.02 81
MK Dons 92.826 14.065 3.457 -72.99 69
Fulham 96.087 14.478 3.500 -75.04 79
Rotherham United 100.652 13.804 3.696 -91.07 71

 

There is virtually no correlation between defensive effort and goals conceded (r = 0.026) whereas defensive efficiency is very highly correlated with goals conceded (r = -0.849). Derby County (89.2), Hull City (85.6) and Middlesbrough (67.2) were the highest ranked teams in terms of defensive efficiency with all three teams being promoted to the Premiership. The lowest ranked teams were Rotherham United (-91.1), MK Dons (-73.0) and Bolton Wanderers (-63.0) with all three teams finishing in the bottom four.

 

So as Championship managers evaluate the early-season form of their teams, the message is very clear to Philippe Montanier at Nottingham Forest, Nigel Clough at Burton Albion, and Owen Coyle at Blackburn Rovers – improve your defence quickly or both your promotion hopes and job security will decline very rapidly.

 

23rd August 2016

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