Photo: dom fellowes
Andrew Robertson, Liverpool’s left back, has been garnering plenty of plaudits for his performances in the Premier League and the Champions League, including a nomination for player of the week in the latter competition. He’s part of the raft of successful signings by Michael Edwards, the onetime analyst who is now the club’s sporting director. But to some, Robertson’s signing was a bit of a surprise:
(By the way, I’d recommend following James on Twitter and reading his always entertaining prose.)
Edwards apparently has a team of up to five mathematics and physics PhDs working for him. What did they see in the young Scottish fullback at a relegated club?
I don’t know what sort of modeling the folks at Liverpool do, but – in the spirit of convergent evolution – it wouldn’t shock me if NYA’s work had some features in common. So here’s a little bit of what I can say about Robertson in 2016-17, which was his last season at Hull City.
In terms of his overall performance, Robertson looked better as an attacker than a defender. His output in attack was close to average for a Premier League fullback, which was saying something when you considered Hull’s modest output as a team. His defending was more mediocre, both in terms of quality and aggressiveness, though it was important to note that he played several times as a wingback. What was happening in front of him also mattered – the likes of Grosicki and Clucas were barely defending at all, which may have put Robertson in tough positions with some regularity. Likewise, with Harry Maguire and Curtis Davies getting pulled to their right to cover the aging Michael Dawson, Robertson would have been left with even more fires to put out.
Yet even if we didn’t adjust for these mitigating factors, Robertson stuck out in 2016-17. He was 22 years old for most of the season. This was well below the peak age band for fullbacks in the Premier League, which I’d estimate at roughly 25 to 29 years old. So his performances would have been expected to improve.
To figure out how much, it’s useful to study other players who were on a similar trajectory. Looking back through earlier seasons for Premier League left backs who were (1) under 23 years old with (2) at least ten full matches worth of playing time and (3) overall numbers as good or better than Robertson’s, I find only the following names:
- Ben Davies, Tottenham Hotspur 2015-16
- Luke Shaw, Manchester United 2014-15 and Southampton 2013-14
- Paul Dummett, Newcastle United 2013-14
- Davide Santon, Newcastle United 2013-14 and 2012-13
- Kieran Gibbs, Arsenal 2011-12
- Armand Traore, Queens Park Rangers 2011-12
This is quite a formidable list. Moreover, the only player who would have been added to the list after Robertson’s final season at Hull was Ben Chilwell, last season at Leicester City. And here’s the kicker: like Shaw and Santon, Robertson would actually have appeared twice on the list, having matched his 2016-17 numbers in 2014-15 as well.
You read that right – if Liverpool’s analysts were doing something similar to NYA’s modeling, Robertson would have been on their radar screen from 2014-15, at 20 years old. He wasn’t necessarily the finished product even in 2016-17, but there was a strong possibility that he was on his way.
I’m sure that wasn’t the end of the story. I can’t think of any sporting director who’d write a check for £8 million based on data alone. It was up to Liverpool to add video analysis, live scouting, physiological assessment, and personality profiling into the mix. I wouldn’t be surprised if Liverpool had a few more PhDs working on those areas, too.