The David Turnbull Archive: An Analytics Love Affair
written by @TheGersReport
The spreadsheets have loved David Turnbull for a couple of years now (even before he made his first team debut). Now that he has completed his big move to Celtic, the pressure will be on for him (the club) to fulfill on the promise that Turnbull put on full display last season.
This post is a look back at when the numbers brought Turnbull to my attention over the past couple of years.
It all began back in 2017 when a certain 17-year old made a list of top midfield prospects I had put together.
In this post, I shared the results of a data based study that was an attempt to flag midfielders with the best potential to be successful moving forward. Goal rates in the developmental league were adjusted based on age & David Turnbull ranked in the top ten for midfielders with at least 1,000 minutes.
Other players on the list? Lewis Ferguson, Jake Hastie, Calumn Morrison, & Mikey Johnston.
Fast forward a summer to 2018 & Turnbull was coming off a two match cameo at the end of the season for Motherwell. It was only 172 minutes of football but the underlying numbers in those games highlighted that the 18-year old was primed to be a break out player.
Here’s what I wrote in July, 2018:
There are small sample sizes & then there's really small sample sizes. Normally, I wouldn't look too much into 172 minutes of football - but Turnbull is a unique case. Ever since he was signed as a nine-year old, Motherwell fans (& fitba hipsters) have been waiting to see what the youngster can do once he breaks into the first team. The debut finally came for Turnbull last season as he featured in two matches.
In those two games, Turnbull proved that he can hold is own at this level. He was directly involved in the creation of seven shots (four shots of his own & three Key Passes). Of those seven shots, five were Scoring Chances (three shots/two Key Passes). That kind of play spiked his Expected Goals numbers:
0.45 xG per 90
0.60 Expected Assists per 90
0.872 xG Chain per 90
Nobody's suggesting these kinds of numbers would last, rather it's evidence that the 18-year old has the talents to contribute & be a key influencer in Motherwell's attack. Look at that xG Chain rate (a stat that aims to give a value to a player's impact on the build-up play leading to a shot). For more on this stat (& why I like it), check out this explanation that I did last summer.
Below you'll find the leaders in xG Chain per 90 last season for players who played 900 minutes or more.
It was only two matches so I'm not going to put THAT much value in what Turnbull was able to do...but it gives you a sense of what it means to average 0.872 xG Chain per 90. You can see there was Stuart Armstrong.....Scott Allan.......and then everyone else. Contributing at that level game in, game out is a real challenge that few could do last season...but I'd like to see Motherwell give Turnbull the chance to see what he can do. It's time...
What makes Turnbull's potential so appealing is the fact he plays in a central midfielder role. So much of the club's attack comes via the wing play of Chris Cadden, Richard Tait, & Elliot Frear - adding Turnbull's playmaking from a central area could really make Motherwell team primed to be a surprise contender for a top five spot in the league.
As the 2018-19 season played out, Turnbull became a household name in Scotland as he regularly seemed to be scoring wonder goals. As our very own Jamie Kilday pointed out…the goal rate is unsustainable & don’t expect Turnbull to replicate it anytime soon. That should not change the narrative around Turnbull. All along, it has been his ability as a playmaker that really has set him apart from many of his peers in the Scottish Premiership.
Back in April, I shared a set of Relative Shot Creation Passing Stats that showed how a teenager was actually outperforming his more adult contemporaries.
Relative Shot Creation Passing stats compares a player’s per 90 passing stats to the rest of the midfielders/wingers on the team.
Below is a list of midfielders & wingers who have the best Relative Key Passes per 90 rates in the league this season (with a minimum of 600 minutes played).
David Turnbull, Motherwell +1.53
Olly Lee, Hearts +1.27
Chris Burke, Kilmarnock +1.22
Scott Wright, Dundee +1.17
Niall McGinn, Aberdeen +1.09
Tony Andreu, Hamilton +1.09
Stevie Mallan, Hibs +1.05
Kyle Magennis, St Mirren +0.87
Cammy Smith, St Mirren +0.81
Ryan Christie, Celtic +0.81
Daryl Horgan, Hibs +0.79
Daniel Candeias, Rangers +0.63
Turnbull’s last appearance in one of my blog posts this season came when I shared one of my favorite stats - Scoring Chance Key Passes. These are the passes that set-up high percentage shots (Scoring Chances). These kinds of shots - kicked shots from the heart of the box & kicked/headed shots from the 6-yard box - accounted for 50% of the goals this past season…despite being only 22% of the shots taken. The Conversion Rate on Scoring Chances was 29%, the rate on non-Scoring Chances was 8%.
It’s my contention that the players who can set-up these kinds of chances give you the best chances of long-term success.
Guess who made the list of leaders?
Here’s what I wrote: (May 2019)
Just a reminder, these are the players who are giving their teammates the best chance to score goals & in turn, the best chance to win matches. The Conversion Rate on these shots is nearly 4x the rate for other shots & if the player taking the shot gets it on target…it’s a 50/50 chance of beating the keeper.
Stats are courtesy of data provided by Ortec Sports.
Who will be the next Scottish youngster to leverage first team opportunities into a big move? I’d say the safest bet is Aberdeen’s Connor McLennan. Like Turnbull, McLennan (19) was first flagged back in the summer of 2017 when, as a 17-year old, he he had the third highest age adjusted goal production for players with more than 1,000 minutes of developmental football. He also showed up in this season’s Scoring Chance Key Passes numbers as being one of the most impactful players in the league…only James Tavernier averaged more per 90 than McLennan.
This was written under the influence of Brent Rademaker.