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 8^th 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 9^th after averaging 1.46 goals conceded per game, the 8^th worst defensive performance in the Championship and only marginally better than MK Dons who were relegated. Fulham performed even worse defensively, having the 3^rd 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

 

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.

 

23^rd August 2016