Don't Listen to Jim White: Adam Rooney Departs Aberdeen at the Right Time
Written by Matt Rhein (@TheBackPassRule)
When news broke that striker Adam Rooney was departing Aberdeen for English National League club Salford City, it became a time of reflection for me. If we flashback to 2015, after learning about the concept of expected goals, I wondered how Rooney's underlying stats compared to his Celtic counterpart Leigh Griffiths. When I found that no one had this data available publicly, I decided it was high time to track it myself and the rest, as they say, is history.
Of course Jim White could not just let me contemplate this and my slow journey to becoming "Yer Da" and instead had to stick the boot into Scottish football. The above tweet is just the latest example of the new genre of Twitter known as "My Gran would score for fun in Scotland." Typically inhabited by English football fans and pundits, it is a bit disappointing to see it from a Scot like White. But rather than get into a pissing contest with the likes of Burnley, Everton, or whatever midsized EPL club fans would inevitably hop into our Twitter mentions, we can show analytically that this is the correct time for Aberdeen to part with Rooney.
I have referenced the idea of a player age curve a few times both on this site and elsewhere, but I wanted to flesh out the idea a bit more. Michael Caley and others have written some very good articles on this concept, but to sum them up, different positions have different ages where a player will be at his peak performance in football. Before that peak age, we can surmise that a player could still improve while if they are past their peak they will likely just regress each year. When looking at the striker position on Caley's age curve, we can see that a striker's peak is typically at 27. Adam Rooney is 30.
Now it is important to point out that Caley's age curve work involved the "big four" football leagues of Europe. I have previously looked at applying the age curve to the Scottish Premiership and found that players both before and after the "peak years" can still find success in the SPFL. So rather than just assuming Adam Rooney has regressed as he got older, we will need to dive into his numbers and see if they suggest he is still performing at Aberdeen's level or is he seeing a regression in his stats?
Unfortunately for Rooney, it is the latter. His goal scoring has slowed down the past few years. In the 2014/15 season Rooney was 26 and right at his peak years as a striker. He had a non-penalty goals per 90 minutes of 0.57, in 2015/16 it was 0.58, in 2016/17 it was 0.30 and last season it was 0.34. While there was a slight uptick last season, Rooney's seen his goal scoring drop every year since his was in his peak age.
Rooney's underlying numbers since then tell a similar story. Though we do not have xG data for that 2014/15 season, in 2015/16 he had an xG per 90 of 0.43, in 2016/17 0.40, and last season it was 0.41 per 90. While this is only a slight regression in xG, we see other stats effecting his performance. He is averaging less shots per 90, averaging 2.25 per 90 minutes in 2015/16, 2.23 in 2016/2017 and only 1.4 last season.
Now this is not to say Adam Rooney cannot serve a club any use. While we have seen him underachieve his xG when it comes to goal scoring, these are still decent goal scoring and underlying numbers for a player his age. He will likely knock in a few goals for Salford.
However, with what we know in general about the age curve for strikers and investigating Adam Rooney's stats the last few seasons, we know he has regressed each year and will likely continue. There are not many scenarios where a club can get money selling a regressing 30 year old striker so, and pardon my French, who gives a shit if that money is coming from a bunch of former players who can't let go of their past glories. Their money is still metaphorically green.
These days it is a lot to ask Sky Sports to get even the basics right about Scottish football. They seem to even struggle determining which crest belongs to which club. So we should not be surprised when their pundits put forth hot takes like Jim White did here, completely devoid of the reality of the situation. Aberdeen did well to get a transfer fee for Rooney. They now should concentrate on finding a replacement for Rooney.
This article was written with the aid of StrataData, which is property ofStratagem Technologies. StrataData powers the StrataBet Sports Trading Platform, in addition to StrataBet Premium Recommendations.