Predicting an ageing pattern for sportsmen as a group is probably one of the most problematic conundrums possible.What seems like a deceptively easy task is actually one that is riddled with pitfalls and selective bias.For example if you want to see how many games on average a 29 year old plays over a season,you can not simply take the record of all players of that age and average the total.The group of 29 year olds is actually a selectively biased sample of players who actually played games during those years.Some 28 year olds may not have played at all during their 29th year,either because they weren't good enough to command a start or perhaps because they were long term injured.So if you are a manager eager to snap up a bargain older player,simply looking at how 29 year olds performed on average will almost always give you an inflated and over optimistic view of how your purchase might perform.
It also seems likely that player position can be an influence on a player's expected decline.Goalkeepers especially managing to achieve to acceptable levels of performance much later in life than the more physical roles played by outfielders.
Of particular interest to Stoke City fans is the question of how the record signing of Peter Crouch will pan out over the anticipated four year duration of his contract.Crouch is a member of a select band of strikers who have scored 100 EPL goals,a testament to both longevity and scoring prowess.So I propose to see how the career profile taken by this select group of players has ebbed and flowed,paying particular attention to the likely amount of games these players can play as they age,how their goals per game ratio changes and how Crouch's career numbers fit into these projections.
|Peter Crouch,a member of the 100 EPL goals club.|
Around 20 players have reached the 100 EPL goals milestone and around half of these players have effectively retired from actively playing top flight football.If we begin by looking at just these retired players,we only have to account for players who are absent from the sample due to dropping out of the top flight and not those who are absent from the older age bands because they are too young.Also as most of the players in this group played the bulk of their games in the early years of the Premiership it might allow us to compare the state of the EPL now to how it was then,for top notch strikers at least.
If we start with appearances.Our sample makeup is biased because we are looking at how players who we know were destined to score at least 100 EPL goals fared in their early years.We hope to mitigate that sample bias by looking at a very narrow band of conclusions,namely how 100 goal players age.We are simply trying to second guess the viability of purchasing proven goalscorers who are in all probability past their best. Therefore,in this initial group of retired players we simply have to account for the players that weren't in the early years and those that drop out of the sample in the later ones.I'll do that by assuming that all players are always present or remain in the group,but if they are no longer playing in the EPL then they contribute zero games for each age they are absent.This process is artificial in the early years because from the limited data we don't know which players will achieve great scoring feats.
These problems also exist in the group of players who are still active in the EPL,but additionally younger players,such as Rooney are not present in the older age groups for the obvious reason.All I propose to do at the moment is to exclude the younger players from the sample beyond their current age and hope that the current batch of older players are reasonably typical of those who will follow.....I did say ageing studies were problematical.
The two subgroups of goalscorers contain around 10 players each,so for an age related season where each striker could play a maximum of 38 games there are 380 potential games available for that age of generational player.If the cumulative total of games played by all the eligible players was say 280,then I've plotted that age band as taking part in 74% of the total available games.
Percentage of Playing Time Seen by Players with 100 or more EPL Goals.
By plotting the average percentage of total available playing time actually played by each group,we can see that current strikers were either asked to or were able to play a higher proportion of league games compared to their earlier counterparts.The sample sizes are small due to the restrictive parameters we've used and the methodology becomes more ad hoc as we see the likes of Rooney dropping out of the batch of current players.But there seems a definite trend for the current top class striker to play more often,younger and this generational gap then starts to narrow at around 28 years of age.Whether current scorers longevity will then dip below the trendline for the previous generation can only be speculated upon,but the current player may well be seen more often earlier and slightly less so later.
Today's 100 goal players,it could be argued are more multi dimensional than previous out and out goalscorers,but a manager seeking to grab an expensive addition to his strike force today will still be expecting goals to be part of the package.We've seen in previous posts that scoring rates can be deceptive,20 goals from 30 games is the same scoring rate as 2 goals from 3 games,but as a seasonal output the former is much preferable to the latter.So when we move on to goal output I've calculated a seasonal rate instead of a rate tied just to actual games played.Potentially players can play 38 EPL league games,so I've used that figure whether they played all 38 or not.When deciding to purchase a player one of the overriding concerns should be how many goals will he add to my teams seasonal total and this approach measures how the pool of players from which we are making our purchase have performed in this respect over time.
Seasonal Goal Rates for EPL Players with 100 or more Goals.
We saw in the appearances graph that the later generation of EPL scorers were seen more frequently,earlier in their careers than had been the case for the earlier generation.So it's not surprising to see the former out scoring their elders,albeit with the gap closing.The current crop of strikers do appear to then be outscored on a seasonal basis by the old guard,however the group does not include any numbers that Rooney may put up post his 27th birthday.So while the trend should be noted,the conclusions are far from being set in stone,Wayne will probably push the green line much closer to the red one once his more mature years are added to the mix..
So how do these graphs relate to what we know about Peter Crouch.
In terms of playing time he appears to be a slight throwback to an earlier generation.Mainly through lack of opportunity he was only playing around 40% of the available top flight games he could have played in his early twenties.So when the currently playing crop of goalscorers are starting to see their playing time decrease at around about 26,Crouch was actually still on an upward curve and he only started to see opportunities decline as he passed 28.Encouragingly he was still capable of playing almost 80% of the available EPL league games when he reached 30.The benchmark figure for top strikers in their 30's is around 75% of league appearances,so Crouch is slightly ahead of the ageing curve but not freakishly so.By 34 when Crouch's current contract expires a typical prolific and long lasting goalscorer was on average still appearing in just over half of his team's league games and,barring catastrophic injury Crouch would expect to do at least as well as this.So 30 plus games in the first year of his contract,dropping to the low 20's by the end seems a realistic estimate for Crouch to achieve,but we really want to know how many goals he'll contribute to Stoke if they continue to invest throughout the side and stay a Premiership side.
This final graph is Crouch seasonal totals expressed in terms of goals per maximum possible number of league games that he could have actually played (this convoluted approach is necessary to account for the occasional 42 game season).A single player sample is going to be more noisy than a larger sample size,but Crouch's goals per 38 game season has been between 0.2 and 0.25 goals per game for all of his later years.These numbers make him a legitimate member of either the Shearer led older group or the Wayneless present collective.
The best case scenario for Stoke fans is that their £11 million record signing has in his dotage the resilience and scoring rate of the earlier group,coupled with the added extras that enables the more recent group to keep being selected despite an apparent decline in scoring ability.In raw goalscoring terms he could reasonably expect to be scoring 12 goals in his first season,falling to around 8 in his final year.Perfectly acceptable returns for a team whose top scorer rarely breaches double figures.