John Harrison Profile picture
⚽️📊🧤Head of Data Science @goalkeeper_com - University of Cambridge Astronomy PhD graduate - Data featured in @TheAthleticFC & @SkySportsPL
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Apr 9 5 tweets 3 min read
Has #Ederson turned a corner regarding his issues with long range 1v1s?

Yesterday he positioned himself perfectly inside his 6yrd box during this long range 1v1 thus allowing his defender to pressure the ball while maximising the finish difficulty for the striker!


#Ederson highlighted how waiting deep is not a passive strategy!

As GKs should only wait deep until the CF gets close enough that the GK will not have enough reaction time to make a save, which is what #Ederson did as he rushed & smothered once the CF was within 14yrd of goal!
Mar 1 6 tweets 5 min read
#DeGea showing how to deal with a long range 1v1!

He initially stays deep & therefore doesn’t gift an easy chip/sidefoot finish by maximising his reaction time!

But once #Antonio takes the additional touch #DDG rushes out quickly & forms the block & snuffs out the shot!

#MUFC If #DeGea had rushed out to engage this touch he would’ve turned a 38% goal probability chance into a 61% goal probability chance as MA could’ve easily rounded him or chipped him!

By waiting he dictated the 1v1 to MA & made him make a decision, MA chose to take another touch…
Feb 28 5 tweets 7 min read
Despite #NUFC’s loss to #MUFC #Karius showed that he is more than capable of playing at the top level!

Our model at #GKxG found his shot stopping was worth 0.22 goals more to #Newcastle than if they had an average #PremierLeague GK in goal

Full article👇… Image #Karius made 8 saves vs #MUFC, but GKing is about quality not quantity!

5 of the saves had xSave>99% thus #PremierLeague GKs save them every time!

The 2 interesting & difficult saves were the 1v1 vs #Bruno & #Weghorst’s long range shot! Which beat #PL GKs 41% & 29% of the time! Image
Jan 3 4 tweets 4 min read
#DeGea continues to be one of the best GKs vs long range 1v1s!

When #Anthony gets in #DeGea doesn’t rush out & gift an easy finish but holds deep & let’s his def recover & pressure the ball!

DDGs top decision making turned a 37% goal probability situation into a 16% one!

#MUFC Gks, don’t always deal with these situations well & often panic & rush out allowing strikers to either chip it over them or curl it round them

Staying calm & letting your defenders pressure the ball & only rushing out once the striker is closer to goal is a vital skill to master
Sep 30, 2022 7 tweets 8 min read
The #PremierLeague is back!

How has your team’s GK performed?

#Pickford’s class shot stopping & distribution puts him top 🏴󠁧󠁢󠁥󠁮󠁧󠁿

#Pope, #Henderson, & #Leno have had great starts at their new clubs🧤

Big mistakes have cost #DeGea & #Ramsdale 😱

#Ward has struggled in all areas 😞 The GK xG model shown above looks at every shot faced, pass received, cross faced & through ball faced & calculates the probability of a goal occurring for & against the GK’s team before the event & after the event occurs!

Thus it measures & evaluates every action a GKs makes!
Sep 30, 2022 5 tweets 8 min read
Will #Potter make #Kepa his number 1?

Most accept #Mendy is the superior shot stopper & shot preventer so the argument is about distributing

We @goalkeeper_com find in recent games #Mendy has been the better passer while both GKs have been equally error prone on the ball!

#CFC ImageImageImageImage When receiving the ball under pressure, both #Chelsea GKs have been below the #PremierLeague standard!

#Mendy has cost #CFC 0.52 xG more than the avg #PL GK would be expected to if they received the ball in the same situations (this is heavily influenced by his mistake vs Leeds) Image
Aug 10, 2022 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, 2022 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, 2022 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, 2022 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