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Wednesday 12 October 2016

EPL: Set Piece vs Open Play (09-10 to 15-16)

I decided to just run some basic analysis on open play and set piece shots/goals, just to have it out in public.  All data is from Opta and whoscored.com. As with many
things on whoscored, certain stats didn't add up but I deciphered the shots and goals into the proper situation and totals. Just so we are clear open play and set piece
are based on Opta's definition. Set piece shots and goals do not include penalties.

Reliability


First thing I like to look at is how reliable a metric is. Given that I only have the year over year stats, this how will we analyze the data.  
Reliability tells us to what degree we can expect a team to repeat its performance of a metric in the next season.



























Open Play Shots For: 79% Skill vs 21% Luck
Set Piece Shots For: 68% Skill vs 32% Luck

We can do a good job of predicting each type of shot situation from one year to the next. If you are a good open play shot team this year
we can reasonably expect you will be good again next year. Same goes for set piece just with slightly less accuracy.

Now the reliability is good know when analyzing teams but we want to make sure that the metrics can explain and/or
predict things that lead to winning. In our case,  goals. 

Explaining Goals For


How well do open play/set piece shots explain goals for in the same season.


















































This is quite interesting.  Open play shots correlate strongly at the end of the season with goals while, surprisingly, set piece shots
have literally no correlation.  Basically, open play shots give you a significantly better indication of what teams scored the most
or least goals in a Premier League season.


Predicting Goals in yr2

Finally, we will see how well open play and set piece shots predict future goals. 




















































Again, we see open play shots providing us with a far superior correlation.  Set piece shots provide us with literally no insight into
future goal-scoring performance. 

This led me to wonder how reliable are set
piece and open play goals?  And how well do they correlate to with Total Goals? What about the conversion rates?

I am not going to plot these but here are the correlations:

Open Play Goals, yr2 vs yr1: r2 = 0.525
Set Piece Goals, yr2 vs yr1: r2 = 0.05

Total Goals yr1 vs Open Play Goals, yr1: r2 = 0.83
Total Goals yr1 vs Set Piece Goals, yr1: r2 = 0.21

Open Play Conv Rate, yr2 vs yr1: r2 = 0.243
Set Piece Conv Rate, yr2 vs yr1: r2 = 0.000




Thoughts

Focusing on open play looks to be the most efficient way to score goals and win football matches. They are more reliable, explanatory, and
predictable at every turn.

Call me Roberto Martinez but I am struggling to see the value in set pieces.  Not only do they not correlate with total goals but
set piece goals are highly, highly variable from one season to the next.  In fact, at best bet we can expect teams to revert right
back to the league average the following year.

Granted this is a very macro look at two sub-groups of shots but at first glance all I am seeing is how much more important open
play is in the Premier League.


Data

Here are the numbers I worked with so you can play around and replicate the findings above.

Year Team Set Piece Total Open Play Total Goals Set Piece Goals Total Open Play Goals Open Play Conv Rate Set Piece Conv Rate
09-10 Arsenal 164 492 79 16 56 0.114 0.098
09-10 Aston Villa 172 317 51 16 24 0.076 0.093
09-10 Birmingham 159 289 38 14 20 0.069 0.088
09-10 Blackburn 224 262 40 21 14 0.053 0.094
09-10 Bolton 218 336 46 20 14 0.042 0.092
09-10 Burnley 133 320 44 4 30 0.094 0.030
09-10 Chelsea 224 598 100 17 70 0.117 0.076
09-10 Everton 186 395 59 17 31 0.078 0.091
09-10 Fulham 151 308 43 9 20 0.065 0.060
09-10 Hull 132 248 39 12 11 0.044 0.091
09-10 Liverpool 175 464 60 14 39 0.084 0.080
09-10 Manchester City 159 362 74 21 46 0.127 0.132
09-10 Manchester United 153 534 76 13 57 0.107 0.085
09-10 Portsmouth 160 367 37 12 16 0.044 0.075
09-10 Stoke 203 197 34 14 16 0.081 0.069
09-10 Sunderland 131 304 48 9 29 0.095 0.069
09-10 Tottenham 210 468 67 17 48 0.103 0.081
09-10 West Ham 168 372 50 18 19 0.051 0.107
09-10 Wigan 156 396 37 10 24 0.061 0.064
09-10 Wolverhampton Wanderers 150 284 31 12 11 0.039 0.080
10-11 Arsenal 168 479 71 9 56 0.117 0.054
10-11 Aston Villa 158 342 46 9 31 0.091 0.057
10-11 Birmingham 137 262 41 16 15 0.057 0.117
10-11 Blackburn 182 269 43 18 22 0.082 0.099
10-11 Blackpool 152 371 59 17 25 0.067 0.112
10-11 Bolton 194 371 50 14 32 0.086 0.072
10-11 Chelsea 219 518 69 18 43 0.083 0.082
10-11 Everton 180 396 52 14 31 0.078 0.078
10-11 Fulham 150 394 53 17 24 0.061 0.113
10-11 Liverpool 147 428 61 11 38 0.089 0.075
10-11 Manchester City 143 394 58 13 37 0.094 0.091
10-11 Manchester United 150 463 76 13 58 0.125 0.087
10-11 Newcastle United 169 333 57 20 28 0.084 0.118
10-11 Stoke 221 258 46 18 21 0.081 0.081
10-11 Sunderland 135 392 43 8 29 0.074 0.059
10-11 Tottenham 203 446 54 12 35 0.078 0.059
10-11 West Bromwich Albion 166 425 58 11 33 0.078 0.066
10-11 West Ham 167 399 43 13 21 0.053 0.078
10-11 Wigan 123 385 36 9 25 0.065 0.073
10-11 Wolverhampton Wanderers 167 289 47 16 24 0.083 0.096
11-12 Arsenal 154 480 79 8 59 0.123 0.052
11-12 Aston Villa 150 285 39 3 29 0.102 0.020
11-12 Blackburn 159 286 47 19 18 0.063 0.119
11-12 Bolton 153 336 43 13 23 0.068 0.085
11-12 Chelsea 169 497 64 14 44 0.089 0.083
11-12 Everton 144 371 51 13 27 0.073 0.090
11-12 Fulham 131 406 45 9 29 0.071 0.069
11-12 Liverpool 170 491 45 14 24 0.049 0.082
11-12 Manchester City 156 574 93 19 63 0.110 0.122
11-12 Manchester United 166 469 89 18 58 0.124 0.108
11-12 Newcastle United 137 349 51 8 41 0.117 0.058
11-12 Norwich 143 369 53 16 33 0.089 0.112
11-12 Queens Park Rangers 140 396 43 11 26 0.066 0.079
11-12 Stoke 152 218 38 16 12 0.055 0.105
11-12 Sunderland 112 344 44 10 31 0.090 0.089
11-12 Swansea 113 353 45 7 29 0.082 0.062
11-12 Tottenham 170 526 66 9 51 0.097 0.053
11-12 West Bromwich Albion 142 399 47 15 25 0.063 0.106
11-12 Wigan 113 399 42 11 24 0.060 0.097
11-12 Wolverhampton Wanderers 125 344 42 9 26 0.076 0.072
12-13 Arsenal 119 473 69 12 52 0.110 0.101
12-13 Aston Villa 107 328 53 10 28 0.085 0.093
12-13 Chelsea 148 468 74 15 46 0.098 0.101
12-13 Everton 181 450 54 11 39 0.087 0.061
12-13 Fulham 106 348 45 8 31 0.089 0.075
12-13 Liverpool 170 564 68 11 50 0.089 0.065
12-13 Manchester City 164 489 66 14 44 0.090 0.085
12-13 Manchester United 131 422 84 22 50 0.118 0.168
12-13 Newcastle United 121 406 45 6 31 0.076 0.050
12-13 Norwich 130 281 43 17 19 0.068 0.131
12-13 Queens Park Rangers 131 365 35 5 19 0.052 0.038
12-13 Reading 122 267 41 13 24 0.090 0.107
12-13 Southampton 126 387 50 8 29 0.075 0.063
12-13 Stoke 149 236 37 15 11 0.047 0.101
12-13 Sunderland 128 285 43 11 20 0.070 0.086
12-13 Swansea 95 411 48 5 41 0.100 0.053
12-13 Tottenham 153 528 63 10 51 0.097 0.065
12-13 West Bromwich Albion 116 382 53 9 33 0.086 0.078
12-13 West Ham 163 326 44 12 26 0.080 0.074
12-13 Wigan 131 368 48 13 28 0.076 0.099
13-14 Arsenal 126 394 70 8 55 0.140 0.063
13-14 Aston Villa 83 344 42 7 25 0.073 0.084
13-14 Cardiff 136 281 30 13 16 0.057 0.096
13-14 Chelsea 135 550 71 15 47 0.085 0.111
13-14 Crystal Palace 120 288 34 8 17 0.059 0.067
13-14 Everton 125 433 62 12 39 0.090 0.096
13-14 Fulham 114 314 42 14 18 0.057 0.123
13-14 Hull 134 292 37 10 21 0.072 0.075
13-14 Liverpool 151 488 102 26 54 0.111 0.172
13-14 Manchester City 165 501 99 20 69 0.138 0.121
13-14 Manchester United 128 393 64 11 46 0.117 0.086
13-14 Newcastle United 132 444 42 8 30 0.068 0.061
13-14 Norwich 117 348 31 4 20 0.057 0.034
13-14 Southampton 132 399 53 12 36 0.090 0.091
13-14 Stoke 96 327 44 7 31 0.095 0.073
13-14 Sunderland 144 341 47 13 16 0.047 0.090
13-14 Swansea 99 392 48 10 32 0.082 0.101
13-14 Tottenham 129 452 53 11 31 0.069 0.085
13-14 West Bromwich Albion 136 348 43 6 31 0.089 0.044
13-14 West Ham 129 291 38 10 24 0.082 0.078
14-15 Arsenal 122 481 70 16 46 0.096 0.131
14-15 Aston Villa 119 297 32 10 19 0.064 0.084
14-15 Burnley 115 312 29 7 17 0.054 0.061
14-15 Chelsea 121 438 73 15 52 0.119 0.124
14-15 Crystal Palace 145 291 46 19 22 0.076 0.131
14-15 Everton 116 360 48 11 29 0.081 0.095
14-15 Hull 118 310 32 7 24 0.077 0.059
14-15 Leicester 130 323 50 12 25 0.077 0.092
14-15 Liverpool 123 461 50 6 35 0.076 0.049
14-15 Manchester City 136 526 85 12 60 0.114 0.088
14-15 Manchester United 121 387 61 12 44 0.114 0.099
14-15 Newcastle United 144 323 41 7 31 0.096 0.049
14-15 Queens Park Rangers 163 367 43 12 20 0.054 0.074
14-15 Southampton 126 381 49 6 41 0.108 0.048
14-15 Stoke 134 365 47 6 38 0.104 0.045
14-15 Sunderland 121 283 35 9 12 0.042 0.074
14-15 Swansea 103 321 44 4 36 0.112 0.039
14-15 Tottenham 132 390 58 15 36 0.092 0.114
14-15 West Bromwich Albion 118 288 37 19 14 0.049 0.161
14-15 West Ham 156 331 45 12 28 0.085 0.077
15-16 Arsenal 129 441 65 13 45 0.102 0.101
15-16 Aston Villa 109 269 28 7 11 0.041 0.064
15-16 Bournemouth 122 338 43 12 28 0.083 0.098
15-16 Chelsea 118 403 57 11 38 0.094 0.093
15-16 Crystal Palace 157 307 42 15 15 0.049 0.096
15-16 Everton 119 367 57 8 43 0.117 0.067
15-16 Leicester 147 362 67 11 46 0.127 0.075
15-16 Liverpool 142 485 63 15 44 0.091 0.106
15-16 Manchester City 167 440 72 14 51 0.116 0.084
15-16 Manchester United 114 313 48 7 34 0.109 0.061
15-16 Newcastle United 77 317 45 8 30 0.095 0.104
15-16 Norwich 115 302 40 10 25 0.083 0.087
15-16 Southampton 127 388 57 13 41 0.106 0.102
15-16 Stoke 96 317 40 6 29 0.091 0.063
15-16 Sunderland 128 308 45 15 25 0.081 0.117
15-16 Swansea 115 321 46 8 23 0.072 0.070
15-16 Tottenham 150 503 71 17 43 0.085 0.113
15-16 Watford 110 329 39 8 21 0.064 0.073
15-16 West Bromwich Albion 118 266 35 12 16 0.060 0.102
15-16 West Ham 171 383 66 16 42 0.110 0.094
Average 142.7 375.8 52.1 12.1 32.2 0.086 0.085

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