Numbers Game: Change brings difficulties to player analysis

Due to rule changes in soccer it can be difficult to compare player performances

To much acclaim, Leicester City's Jamie Vardy has claimed the English Premier League record for goals scored in consecutive games. It is good, then, that Jimmy Dunne's 1931/32 streak of scoring in 12 successive top flight games is getting some media attention. The Irishman holds the record in English top flight soccer, after all. Is it right to sacrifice pre-1992 soccer history to the breathless glory of the Premier League?

Soccer wouldn’t be alone in changing over the last 100 years. The NFL introduced the forward pass; the NBA, the three-point line. Cricket has just played its first day/night Test match. For historians and number-crunchers such changes provide a challenge in asking how good a performance was compared to those from the record books.

Dan Daly, longtime sports columnist with the Washington Times, speaking about the NFL, said sports fans tend to live in the present and "lots of the younger sportswriters don't tend to pay attention to things that haven't happened in their own lifetimes".

In considering players past, one must also consider a changed game. “If you can find anyone, say, pre-1960, who’s doing something comparable statistically to what they do now that’s just off the charts.” In English soccer, that works the opposite way.


While English top-flight soccer has seen goalscoring peaks and troughs from season to season, on the all-time list of English top-flight goalscorers a disproportionate number enjoyed careers spanning the 1925-1935 seasons. It was a time of goalscoring gluttony where goals were scored a third more often than today. In 1925/26 two players would keep a player onside, rather than three.

Top-flight game

This change resulted in a sudden and sustained jump in goals from that season onwards with the rate falling over time only to jump again in the 1950s. Since the late 60s (a time when the tactical substitute was introduced) the average number of goals per top-flight game has on the whole remained relatively level.

Dixie Dean

and other goalscorers between the two World Wars were dancing to a different footballing tune.

How can one define an “era” in sport? Some potential dividing lines that influential sports analyst Bill James set out in a 2012 essay are useful. Have there been rule changes? Structural changes? Changes in how the game is played? Radical changes in statistical standards? Significant external events? Each of those boxes has been ticked at various times in English soccer history.

Examples: that 1925/26 offside change; the arrival of the Champions League; fashions changing from five forwards to one over the course of a century; the scoring rate of the 1930s; English clubs being banned from Europe in the latter half of the 1980s.

There are many examples for each, and perhaps a host of small changes add up to something much more significant.

Comparing performances

This week when asked by

The Irish Times

about comparing performances against history James provided answers that were both straightforward and insightful.

Summarised: when defining eras, what might seem to be a momentous, instant change can take time before an impact is actually felt on the field. Also, many tiny changes can over time add up to a huge change. And just because it is impossible to make a model perfectly accurate, one should not be afraid to try.

Fundamentally, if 1920s Dixie Dean were to be transported to the Goodison Park pitch in 2015 he’d know this was a game of soccer. The offside law will have changed again and the backpass disallowed. The professional foul and the rash tackle from behind would be red card offences. There would be substitutes, to be chosen from a large bench. And foreigners all over the field. But at its heart it’s still a game of soccer and he’d know how to play it.

So we get back to Jamie Vardy. The past should not be cast aside but instead used to add another layer to the game we watch today. The Leicester striker’s 14 goals are 73 per cent of the average Premier League team’s 19 so far this young season. Only one player in English top-flight history has surpassed that over a full campaign; Dixie Dean’s 60 goals in 1927/28 (75% of the average team’s 80).

It may well be that soccer is fundamentally different since 1992. But, if so, that’s more likely to be because history will look back at the introduction of backpass law that same year, along with other changes since, as having more significance than the relaunch and renaming of a sports competition.