Thursday, 28 January 2016

Happy Birthday, Peter Crouch.

It is nearly a year since I had the pleasure of helping Simon Gleave in putting together a presentation at the 2015 OptaProForum. The presentation looked at the ageing curve within the Premier League, so I thought I'd take advantage of the upcoming anniversary to reprise the theme.

But first.

Tuesday night saw the conclusion of a largely low quality league cup semi final between Stoke and Liverpool, won after extra time and penalty kicks by the Reds.

The tie, particularly the second leg was awash with narratives waiting to be seized upon by the commentators and pundits.

Corner kicks, we were told were Liverpool's weakness and Stoke's strength (circa 2010, maybe). Could the beleaguered Benteke redeem himself as a second half sub. Might Stoke's, Everton supporting Jon Walters score against their Merseyside rivals or Klopp march the Reds to new heights, despite barely shifting the statistical performance dial.

Once the game went to extra time and especially following Flanagan's red card substitution, penalty kicks became the focus of attention and it was left to Twitter to propagate the by now hoary old myth that the team shooting first wins 60% of the time.

Stoke had that privilege, promptly lost and all that was left was for Klopp to pronounce Liverpool deserved victors on the night. Rose tinted, rather than new designer specks.

One of the many possibly story lines did actually unfold. Peter Crouch ex Liverpool missed in the shootout for Stoke, although the media for once failed to demonise a player for failing with an opportunity that is missed around 20% of the time.

Crouch is nearing the end of a highly successful career. He will be 35 on Saturday, when Stoke take on Palace in the FA Cup. Save for a couple of formative seasons bouncing around the loan circuit from the Isthmian, to the Swedish and finally the English second tier, he has played exclusively in the Premier League for a variety of clubs.

Spurs, Liverpool, Villa, Southampton, Portsmouth and currently Stoke have all enjoyed the benefits of  6'7" Crouch being "much better on the ground than you give him credit for".

"The Windmill", Crouchie's short lived follow up to "The Robot".
The general ageing profile for out field Premier League players follows a path of gradual improvement through physical maturity and greater experience. Before the former leads to a decline in the physical side of the game that eventually cannot be compensated by an increase in the latter.

27 or 28 appears to be the stage when a player is at a peak and thereafter a decline in performance becomes likely.

A bell shaped plot, often using playing time as a proxy for performance neatly demonstrates the rise and fall of a players career path.

An alternative is to chart the changing output of a player from one season to the next. A young player will gain more playing time if he followed the hoped for progression, reaching a peak before an age related decline sees the opportunities given to him begin to decline.

This approach may not produce a clean plot if applied to the career of a single player. Long term injury may eliminate large portions of a season for one player compared to a much larger sample of like for like players. Or a player may fall out of favour, while remaining cushioned by a favourable contract.

In the case of Peter Crouch, the level and squad competition for places was likely more fierce at Liverpool and Spurs compared to Portsmouth and Southampton in their relegation year.

Therefore, if minutes played is used as a proxy for performance, the level of the club at which those minutes were earned should form part of the calculation.

2690 Premier League  minutes as a 31 year old in a Stoke team that earned 45 points has to be measured against 2141 minutes as a 24 year old in an 82 points Liverpool team.

In the plot above, I've created a performance indicator that combines minutes played and the quality of the team in which those minutes were won by the player. I've then plotted the change from season to season and although the plot is inevitably noisy, the trend line is typical of the gradually declining improvement until aged 28, followed by season on season decline until the mid 30's signal a possible need to consider options outside of the Premier League.

Crouchie's performance trend line neatly begins to turn negative around 28.

The noticeable dip in the individual plotted points at 25 is Crouch's final season at Liverpool under Benitez and in competition with Torres.

The January transfer window is perhaps not the best time to turn 35, an asset depreciating before your very eyes, but Crouchie will delight the Stoke fans if he scores the winner against Palace, if selected in the 4th round of the cup.

Sorry, Simon.

No comments:

Post a Comment