Expected Goal

Discussion in 'General football forum' started by Saddleworth2, 11 Aug 2017.

  1. Saddleworth2

    Saddleworth2

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    This from the Daily Fail, reporting on the introduction of an expected goal metric to Motd this season

    So, what is an expected goal?

    An expected goal is a way of working out the percentage likelihood of a player scoring from a position on the pitch.

    It is a new analytical tool provided by Opta which shows how many goals a player or a team should have scored based on the chances they had in a game or over the course of a season.

    Each chance is ascribed a 'quality value' (xG) based on thousands of chances analysed by Opta over the history of the Premier League.

    The higher that figure - and one is the maximum value - the more likely a chance will be converted.

    What can they tell us about players?
    It is a very good way of establishing whether a player is scoring more or less goals than his chances should dictate.

    So, for example, a striker could finish as a club's top scorer, but he might actually be one of the weaker finishers in the side.

    It also lets a fan judge at a glance whether a striker is an elite level player or whether he is simply being bolstered by the creative talents around him in the team.

    Each of last season's top eight goalscorers, barring Sergio Aguero, scored more goals than their expected goals would suggest likely. This means that each of them are expert finishers.

    And for 29-goal Harry Kane, who scored over 10 goals more than expected, it flags him up as a world-class striker.

    The same system applies to players who are performing worse than expected. It allows you to flag up whether a player is being wasteful in front of net, beyond someone in the pub saying, 'He had to score that!'.

    ACTUAL GOALS V EXPECTED GOALS
    Player Actual goals /Expected goals (xG)
    Harry Kane 29/ 18.6
    Romelu Lukaku 25/ 15.3
    Alexis Sanchez 24/ 17.6
    Sergio Aguero 20/ 20.5
    Diego Costa 20/ 14.2
    Dele Alli 18/ 13.3
    Zlatan Ibrahimovic 17/ 14.4

    What decides the likelihood of a goal?
    Opta have analysed over 300,000 shots to calculate the likelihood of an attempt being scored from that specific position on the football pitch.

    That has also included what phase of play the chance comes along in.

    These are the key factors:

    • Distance from goal
    • Angle of the shot
    • Was it a shot or a header?
    • Has the player just gone around an opponent?
    • Was it a one on one or were defenders involved?
    • What was the assist like? (e.g. long ball, pull-back, cross, through ball)
    • In what part of the game did the chance occur? (e.g. open play, direct free-kick, corner kick)
    • Is it a rebound?
    And how does it help us judge a team?
    It lets an analyst judge a team's future performances if their current results are not matching up to displays.

    Say there is a team that is dominating matches and making a ton of chances but losing or drawing more frequently than their play would suggest.

    Sometimes that would mean a manager would be up for the chop. Expected goals lets that fear disappear to an extent and proves that a turning point is likely to just be around the corner.

    Juventus in 2015-16 are an example cited by the BBC. They won only three of their first 10 games but analysis shows they were vastly outperforming that level of results.

    And after a turning point came, they eventually cantered to the title. Expected goals can be a valuable tool for fans, journalists and pundits alike.





    Basically this stat is saying the Kun is scoring what you would expect him to score based on the quality of chances he is getting, but of the top 7 goalscorer, he is the only one that hasn't scored more than their 'expected goal' score.

    I guess my reaction to that is its probably validating what we saw with our own eyes, he is a great striker but he misses chances and doesn't really score the worldies he maybe once did because he has dropped a little in pace. If you look at what it says about Kane, again it smacks of the truth. He does score a lot of goals that you would rate as half chances. Will be interesting to see how this stat develops as it can also be applied to whole teams as it was to Juventus in the example given. I bet we didn't beat our expected goal score last season!
     
  2. yeah whatever !!

    yeah whatever !!

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    I expect MOTD pundits to be shite and am right 100%..

    This is easy.
     
  3. Saddleworth2

    Saddleworth2

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    Yeah, but that was an expected insult!
     
  4. vmsuhail

    vmsuhail

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    I remember only 2 great goals from Sergio last season - the one against Monaco and the one he scored from a very tight angle in a game we were down to 10 men (don't remember the opposition)

    Didn't watch Everton last season, but It's a bit concerning to see Lukaku has scored 10 more goals than expected.
     
  5. yeah whatever !!

    yeah whatever !!

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    Not insulting you fella by any means, just the MOTD( mumblings of the dinosaurs) team.

    It seems to me they want to have more reason to justify themselves as pundits.

    The best pundits are the fans.
     
  6. Saddleworth2

    Saddleworth2

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    No, don't worry, didn't take it as that!

    The stats are from OPTA but no doubt they will be mangled out of shape by those that steal a living on MOTD.
     
  7. yeah whatever !!

    yeah whatever !!

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    No doubting that mate.
     
  8. Saddleworth2

    Saddleworth2

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    This taken from an article in the telegraph last month:


    City will fly if Ederson is a success

    One of the big reasons for why Manchester City failed to challenge for the title last season was their lack of a convincing goalkeeper.

    City were second bottom in the whole division in 2016-17 when looking at actual saves made compared to expected saves (xS).

    According to STATS, xS "estimates the likelihood that a shot will end up as a goal based on the player’s position and shot location", and City were -6 when xS were subtracted from actual saves made.


    This means Claudio Bravo and Willy Caballero between them let in six more goals than the average Premier League goalkeeper would have been expected to. Only Crystal Palace had a worse ratio.

    [​IMG]
    CREDIT: STATS
    Tottenham, who finished a place above City, by contrast saved 10 shots more than they were expected to.

    The difference therefore between Hugo Lloris' heroics and Bravo and Caballero's travails was 16 goals. If City's new £34.7m goalkeeper Ederson can eat into that differential, then City should make a much better fist of a title challenge this season.

    City were also second best in the table for Expected Goals Against (xGA) but in reality conceded the fourth most goals in the league. Individual defensive errors were a factor here, and Pep Guardiola will be hopeful that his summer overhaul of City's full-backs will improve the situation.

    [​IMG]
    CREDIT: STATS
    Guardiola's team were also one of the most wasteful teams going forward and were only 13th when subtracting expected goals from actual goals scored. This is pretty remarkable given their attacking players included Sergio Aguero, Kevin De Bruyne and Leroy Sane.

    Having Gabriel Jesus fit and settled, coupled with the arrival of Bernardo Silva should improve City in this regard this season

    [​IMG]
    OK, all that does is state what we know we saw e.g., poor goalkeeping and wasteful in front of goal, but good to see it laid out in stats. Vindicates Pep as well.
    Have every confidence that we will fix the poor goalkeeping this season. Underlines the need for more firepower though.
     
  9. Vienna_70

    Vienna_70

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    We conceded the fourth least goals in the League.

    Only Chelsea, Spurs and the rags let in less.
     
  10. Saddleworth2

    Saddleworth2

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    Yeah, that quote just looks wrong doesn't it.
     

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