John Harrison Profile picture
☄️🔭🌟University of Cambridge Astronomy PhD graduate - Head Data Scientist @goalkeeper_com - Data has featured in @TheAthleticUK & @SkySportsPL🧤⚽️📊
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Aug 10 8 tweets 5 min read
A GK’s handling ability is vital & often under analysed!

Here #DeGea showed how handling can determine a game’s outcome when he parried a 49mph central shot into danger & the rebound was scored!

xRebound xG = 0.09
Actual Rebound xG = 0.47

xG added due to poor handling = 0.38 My handling model uses historic shot data to gauge how often certain shots should be expected to be caught, parried away from danger, & parried into danger in combination with a none shot xG model which assesses how likely rebounds are to be scored based on the parry location
Jun 14 6 tweets 5 min read
Not a good night for #Ramsdale!

The 4th goal summed it up!

-Engaged the 1v1 when it was 20yrd out & there was a CB covering making the finish far easier

-Using the smother technique rather than the spread technique making the chipped finish far more difficult to save

#ENGvHUN ImageImageImageImage My 1v1 model shows that engaging 1v1s at distances greater than 14yrds from goal just makes the finishes easier rather than harder

The best GKs (like #Alisson) often wait deep & lure the striker in & then engage the ball once they know they can snuff out the shot!

Jun 7 10 tweets 11 min read
My 1st @goalkeeper_com piece:

How many goals were the big 6 GKs worth vs the avg #PL GK?

#Alisson was worth ~19 goals! What more does a GK have to do to get #POTY!

#DeGea was the best shot stopper but his weak shot prevention & distribution meant he was only worth ~3 goals! #Ederson was the best distributer & his shot preventing was class but his below average shot stopping means his value is far below #Alisson’s!

#Ramsdale’s performances at the end of the season were average but his incredible start means he ended the year with great numbers!
Feb 9 6 tweets 5 min read
#DeGea struggles with close range 1v1s continue!

His decision making is good, as he doesn’t engage too soon & only engages once he cannot to react in time to the shot, but his problem is, as always, the way he twists his body away from contact which leaves gaps in his barrier! ImageImageImageImage My model finds that if #DeGea had engaged the 1st touch the chance would’ve been 0.64 ExG because even though the 1v1 is quite far from goal engaging in that location would make the GK very vulnerable to the chip, sidefoot finish, and being rounded. Image
Dec 30, 2021 17 tweets 15 min read

Today I’ll breakdown #DeGea’s performance in the #PremierLeague using my bespoke GK models!

The headline is for the first time in 3 seasons #DeGea’s shot stopping skills are outweighing his weak shot prevention skills & thus far he has saved #MUFC ~5 additional goals! Image Shot Stopping:

#DeGea’s shot stopping has been world class, my model predicts he has saved #MUFC ~5 goals more than an average #PL shot stopper would’ve thus far!

The goalmouth map highlights just how hard #DeGea has been to beat, if you don’t hit the corners you won’t score! Image
Dec 24, 2021 16 tweets 15 min read

How good has #Ramsdale been for #Arsenal so far?

I’ve seen him described as both “the signing of the season” & “a camera save merchant” but what does the data say?

In this thread I will breakdown his performance in all areas of goalkeeping using my bespoke models

#AFC Shot Stopping:

#Ramsdale’s shot stopping has been excellent, my model predicts he has saved #AFC ~3 goals more than an average #PL shot stopper would’ve thus far!

He’s basically only conceded vs close range shots in the corners & has pulled a few shots out of the top corners!
Nov 3, 2021 11 tweets 9 min read
Last night was rough for #DeGea

The 1st goal was a textbook shot stopping technique selection mistake

The shot went next to DDG’s right foot but rather than go with his foot he went with his hand

It was odd to see as DDG’s shot stopping technique selection is usually flawless! I actually thought #DeGea’s footwork before the shot occurred was excellent & it got him into a great position to make the save but his shot stopping technique selection let him down at the last moment & meant he couldn’t make the save!

Nov 1, 2021 4 tweets 4 min read
My models view of #Ramsdale’s FK save:

He was well positioned as he was stood on the line between the ball & the outside of the wall!

It was a good, but not unbelievable, save. My model finds such a FK gets saved ~50% of the time due to its low speed & distance from the post! Image I’ve seen the save described on Twitter as both the save of the season & poor positioning followed by a slow recovery!

As usual the truth is between the two & I should make it clear here that saving a 50/50 shot is a lot closer to the save of the season than poor GKing!

#AFC Image
Oct 29, 2021 9 tweets 8 min read
#DeGea’s ability to deal with crosses has quite rightly been criticised.

In the #PremierLeague #DeGea has only prevented 6 opposition chances occurring by claiming crosses!

My model finds this lack of activity means #MUFC concede on average an additional 0.14 ExG every game! In comparison #Alisson of #LFC has prevented 18 opposition chances occurring by claiming crosses & #Alisson has played 90 fewer minutes!

This difference in cross claiming ability corresponds to #LFC facing on average roughly 0.36 fewer ExG per game in comparison to #MUFC!
Oct 23, 2021 4 tweets 4 min read
I’ve seen this describe as a wonder save but it’s a decision making error followed by a good recovery

My 1v1 model predicts this to be scored 2% of the time if the GK holds deep while if the GK rushes, like #Mendy, it is scored 64% of the time

He made it way harder for himself! I think #Mendy is a top GK by the way & he’s made many great saves this season but just because a GK is good doesn’t mean we should praise them regardless of how good their goalkeeping actually is!

Outcomes shouldn’t dictate analysis, processes should!
Oct 23, 2021 4 tweets 4 min read
#Ramsdale’s distribution last night was unreal!

All 12 of his open play passes resulted in unpressurised #AFC possession & made it more likely that #AFC scored next!

Additionally 7 of those passes successfully broke #AVFC lines & took multiple players out of the game!

#FNF What a ball this was

It’s unbelievable awareness to spot the run, then exceptional technique to pick it out!

Being able to set up 2 v 3 situations from the GK is so useful

This pass was certainly the standout moment for me but importantly it was not an isolated incident at all
Oct 22, 2021 4 tweets 2 min read
Ah I feel for #Martinez, shuffling around on his line pre shot & ending up on the left side of his goal cost him those extra inches that would’ve allowed him to parry the ball away from danger!

At the same time it was potentially the movement that put PEM off so it’s a hard one! Obviously it was a top top penalty save but you could instantly tell by #Martinez’s reaction that he was gutted with the fact he didn’t manage to push it out wide.

I don’t think #Martinez should be too harsh on himself thought as I think it was just smart timing from Auba
Oct 22, 2021 4 tweets 3 min read
What a forced out of position 1v1 save from #Martinez!

His foot speed to get across is excellent & his decision to dive left pre-shot to get his body in-line with the ball is also class!

This was Emi’s 5th FOOP 1v1 save since 19/20!

No #PL GK has made more!

#AVFC #AFC #FNF Definition: A forced out of position 1v1 is a 1v1 which occurs either after a rebound, ricochet, or cross which results in a 1v1 situation where the GK could not possibly be inline with the ball as the situation starts & needs to reposition quickly to make the save
Oct 21, 2021 7 tweets 4 min read
I don’t often post videos of myself playing but given I dropped a 15 save MotM performance for @oldthorntonians last weekend I thought it would be interesting to post my favourite 4 & run a poll to see which save people think is the best!

(See thread below for videos)

#GKUnion Save A:

I particularly enjoyed my pulsing feet & constant little readjustments pre save & use of the collapse dive to make this save. I also enjoyed how I manipulated the ball & guided it out for a corner rather than putting it back into danger.
Sep 30, 2021 5 tweets 4 min read
This is my favourite #DeGea #UCL save from yesterday

Because it didn’t require athleticism or reflexes it required calmness & good decision making!

38% of the time a 1v1 in that position results in a goal but after DDGs decision to rush back to his line & wait this falls to 7%! ImageImageImageImage #DeGea showed you don’t need to start deep to get into such a position, he was over 12yrd out & was ready to sweep if he had to but because he made the decision to drop & react so quickly & confidently he managed to use his wonderful fast footwork to get back in time.

#MUFC #UCL Image
Aug 22, 2021 6 tweets 6 min read
#DeGea is one of the best GKs in the #PremierLeague when dealing with long range 1v1s & the save vs #Armstrong was great!

He knew AA was ~15yrd out so it would take a top finish to beat him so he didn’t need to rush out or gamble as that would only make AA’s finish easier

#MUFC ImageImageImageImage It may look like a simple save in the end but that’s all down to #DeGea’s excellent decision making which massively reduces the chance quality

The composure DDG showed to stay deep to his line & not over commit early isn’t common, even in the #PremierLeague

Such top goalkeeping Image
Aug 19, 2021 9 tweets 9 min read
THREAD: #Ramsdale to #Arsenal

It will be interesting to see how #Ramsdale gets on at #AFC & how his game evolves.

One thing #AFC know they are getting is a quality 1v1 stopper!

My model suggests #Ramsdale’s 1v1 prowess saved #SUFC ~3 goals more than an average #PL GK would’ve! In comparison #Leno was average at stopping 1v1s last year & given the brand of football #Arsenal wish to play maybe this was in their thought process when they scouted #Ramsdale.

My model has #Ramsdale as one of the top 5 1v1 stoppers in the #PL & potentially can still improve!
Aug 16, 2021 4 tweets 3 min read
Project Preview:

This #AlexanderArnold FK against #Chelsea was the most unstoppable FK in the #PremierLeague since 2017/2018 according to the FK ExSaves model I’ve built!

My model predicts this shot would only be saved 6 times in 1000!

& Trent made it look so simple!

#LFC #GK ImageImage For those interested, this graphic is a good representation of what the model actually “sees”.

The variables used to train the model were:

• Initial Shot Distance
• Initial Shot Angle
• Shot Trajectory Relative to the Wall
• Final Shot Location
• Shot Velocity Image
Aug 14, 2021 5 tweets 6 min read
Class from #Alisson!

Wonderful decision to wait & react rather than engaging #Pukki!

#Alisson’s improved so much vs long range 1v1s!

19/20 long range 1v1 ExSaves: 6.01
19/20 long range 1v1 Saves: 5 ❌

20/21 long range 1v1 ExSaves: 11.46
20/21 long range 1v1 Saves: 13 ✅

#LFC ImageImageImageImage So many GKs panic when strikers run in 1v1 (& #Alisson used to be one of them) & feel they have to rush out & immediately & end up gifting easy finishes.

It’s awesome that #Alisson seems to have fixed this weakness in his game because his compatriot #Ederson still hasn’t! 👇🏻
May 18, 2021 8 tweets 7 min read
What a save from #DeGea

Unbelievably calm GKing in a crucial moment

It may look like a simple save but that’s all because of his exemplary decision to use the wait & react 1v1 strategy as the 1v1 was from long range!

Not many GKs could make such a good decision

#MUFC #MUNFUL The striker was ~16 yrds from the centre of goal & at a pretty wide angle (hard to see from the photo) so #DeGea’s decision to stay deep made the finish very difficult as he didn’t rush out & gift a simple dink/rounded finish
May 7, 2021 6 tweets 6 min read
After showing us how a GK can maximise their chances of saving a close range 1v1, #Schmeichel has just show how us how a GK can minimise their chances of saving a long range 1v1!

By engaging early he allows Wilson to easily round him with 1 touch!

He needed to wait for longer! If #Schmeichel waits inside his 6 yard box for #Wilson’s touch, #Wilson then has a decision to make:

1. Shoot from 17yrd knowing defenders are track back.

2. Take a touch knowing he will bring it closer to goal but also closer to the GK.