One of the surprise packages during the Premier League this season has been the performances of Sheffield United who, with only eight games left to play, are in serious contention for the European places. The newly promoted side have particularly impressed defensively, with only Liverpool conceding fewer goals (21) than The Blades this season (28). A player who has had a significant role in this success is their 23-year-old goalkeeper, Dean Henderson, who is on his second season-long loan from Manchester United.
Despite his ineligibility to face his parent club tonight, there will be a lot of speculation about the future of the number one jersey at Manchester United. As Roy Keane gracefully eluded to in the Sky Sports Studio at half time on Friday, David de Gea played an unfortunate role in Tottenham’s goal to reignite the goalkeeping debate at Manchester United, and some curious eyes have shifted towards Bramall Lane for a closer look at their loanee’s performances for Sheffield United this season.
Evaluating Goalkeeper Performance
There is no doubt that Dean Henderson has had a fantastic season with Sheffield United, recording the third best save percentage in the Premier League (76%) and keeping the joint-most clean sheets (11). However, evaluating goalkeeper performances using traditional metrics like these has its limitations, as these numbers can be heavily biased by team and defensive strengths. If you’re in goal behind the best defence in the world, you would expect to perform highly in these metrics regardless of your abilities as a goalkeeper.
More recently we have been able to isolate an individual goalkeeper’s performance using our expected goals on target (xGOT) model. Using this model, we can predict how many goals a goalkeeper would be expected to concede, given the quality of the chance (xG) and the end goalmouth location of the shot. As a result, we can directly evaluate the contribution of the goalkeeper and see how many goals they prevented for their teams.
Dean Henderson was expected to concede nearly 33 goals this season, according to our xGOT model. Given that he actually only conceded 25 goals (excluding penalties and own goals), the young English goalkeeper prevented nearly 8 goals with his saves this season, a phenomenal tally only exceeded by Newcastle United’s Martin Dubravka (8.7) and Crystal Palace’s Vicente Guaita (9.6).
While “goals prevented” is intuitive, the inevitable rebuttal here is that goalkeepers who face more shots have an opportunity to prevent more goals. To allow for a fair comparison between goalkeepers, we can standardise for the number of shots each keeper faced by looking at their goals prevented rate (xGOT conceded divided by goals conceded).
Dean Henderson’s goals prevented rate of 1.31 this season means he was expected to concede 1.31 goals for every goal that he actually concedes. Henderson again performs highly in this metric, ranking third in the Premier League this season.
A quick look at tonight’s foe, David de Gea, shows that the Spaniard has conceded nearly one more goal than the average goalkeeper would be expected to concede this season:
While xGOT is a great measure of an individual’s performance in comparison to the ‘average’ goalkeeper, each goalkeeper in the league will face different types of shots over the season. These shots will be influenced by the defensive style of their team and the opponents they face and hence, may or may not be favourable to an individual goalkeeper’s strengths and weaknesses.
However, using Stats Perform’s Goalkeeper Index, we can now personalise these estimates to each goalkeeper and simulate how they would perform over the exact same sample of shots.
How Does The Stats Perform Goalkeeper Index Work?
The Stats Perform Goalkeeper Index uses AI modelling techniques with several descriptors to capture the influence of a particular goalkeeper on the shot outcome.
On top of the start and end location of the shots, the Goalkeeper Index personalises the predictions by considering a goalkeeper’s historic ability to save shots based on factors such as:
- Shot destination (left, middle or right segments of the goal)
- Angle to the shot trajectory (straight at them, to the left or to the right)
These features capture goalkeeper strengths and weaknesses on a high level and act as proxies for factors such as handedness, anticipation, and reaction time for shots of varying angles and destinations. We use these features on a season level and as a 10-game rolling window average in order to capture the current form of the goalkeeper.
What Do the Rankings Look Like This Season?
Using the Stats Perform Goalkeeper Index, we can simulate how each goalkeeper would perform if they faced all 2,550 of the shots faced by goalkeepers in the Premier League so far this season. This gives us the number of goals that each goalkeeper would be expected to concede. To make this more interpretable, we can standardise these values to a game by game value and compare this performance to the league average.
We find that David de Gea ranks second highest in the Premier League and is expected to prevent 0.19 more goals per game than the league average. Meanwhile, Dean Henderson ranks in a respectable seventh place, preventing 0.08 goals over the league average. The rankings indicate that David de Gea may have faced some unjust criticism of his abilities over the weekend, given that the model suggests that only Alisson has been a better goalkeeper this season.
While goalkeeper errors are more costly than others, and certainly not a trait you want in your number one, pundits and fans are often quick to judge goalkeepers on their recent mistakes and bias their evaluations of a player towards these negative actions (one for the “form is temporary, class is permanent” crowd).
What’s Next For Dean Henderson?
David de Gea, the experienced 29-year-old Spanish international in the way of Dean Henderson at Manchester United, is unlikely to be on the move in a summer that is expected to see caution in the transfer window, particularly given his previous suitors at Real Madrid and PSG seem to have finally established some consistency with their goalkeepers in Thibaut Courtois and Keylor Navas, respectively.
Dean Hederson has been very vocal about his future ambitions to be both the number one for his parent club and his country. It is a belief that it backed by many, including the Manchester United manager himself, Ole Gunnar Solskjaer, who echoed these aspirations during his press conference via Zoom yesterday:
“I think Dean has had a fantastic couple of years at Sheffield United and I think eventually he will end up as England and Man Utd number one.”
As the second youngest regular Premier League goalkeeper (behind only Bournemouth’s 22-year-old Aaron Ramsdale), Dean Henderson still has plenty of time on his side to cement his inevitable place between the posts for Manchester United and England.
To further fuel his ambitions, the postponement of Euro 2020 could be a blessing in disguise for the 23-year-old. While it was likely to be premature this summer, another full season of Premier League football could see Dean Henderson mount a serious challenge to Everton’s Jordan Pickford place as England’s starting goalkeeper in the rescheduled tournament next year.
There is a strong likelihood that Dean Henderson will spend another season out on loan to gain more valuable playing time and, much to Roy Keane’s disappointment, we would expect to see David de Gea continuing to take the Manchester United team bus home next season.