After Liverpool’s exhilarating draw against Manchester City on Sunday, one or two commentators were quick to comment how Brendan Rodgers’ Liverpool are “undeniably progressing” this season. In fact, the entire managerial narrative arc under Rodgers’ Liverpool depends on the notion that once Liverpool adapt to his style perfected at Swansea, the club will return to the former heights of glory.

Borrowing a method from James Grayson, I plotted the rolling average of Liverpool’s total shots ratio (TSR) this season against their per-game PDO. Liverpool’s PDO averages to 1000, remarkably straight down the middle. They’re not particularly lucky or unlucky, but this average is slightly below that which you’d expect of a league-leading side.

Their TSR meanwhile has plateau’d around the .615-.620 mark. That’s an improvement over their Christmas TSR average of .608 (as Grayson has written, TSR has predictive power in as little as 4-6 games), but it’s also similar to the average Liverpool ended up with last season under Kenny Dalglish (.619). For comparison, Man City finished with a TSR of .654 last season.

Liverpool’s run of recent form may not seem that impressive considering the improvement in these numbers, but two draws against Arsenal and Man City respectively, preceded by three wins against smaller sides with a loss to United thrown in, indicate Liverpool could improve on their current 7th place position a little bit.

Comments (14)

  1. I know anfield has all that history but they need to expand it or something, if theyre going to compete they need higher ticket revenue or for fenway to do what they did with the sox and become what they hate the most, for the sox it was becoming the yankees, liverpool needs to become man united. the evil empire, spend spend spend, debt, debt, debt, win, win, win.

  2. I don’t necessarily feel that Liverpool need to spend so much in order to achieve the glory that the history of the club deserves. It’s clear to see for all, that Liverpool have improved by a fair bit over the season so far. I think they only need a few more signings to push them into top 4 contenders. And from there, it’s only a matter of time before they start fighting with the big boys for the title.
    However, I do agree that they should probably do something to expand Anfield (like United have done with Old Trafford over the last few decades) in order to generate revenue and more interest in the club.

  3. Liverpool have spent loads of money over the past few seasons. Many of those players haven’t lived up to those price tags.

  4. What’s a PDO please?

  5. “Liverpool could improve on their 7th place a little bit” – Incisive and ground breaking as ever…

    • The point was that the underlying factors behind the way Liverpool’s improvement indicate they might be a better team than their table position suggests. But that was clever I guess, so bravo?

  6. Yeah, i’m with Jeff. Wanna share what PDO stands for, or are you intentionally keeping it a secret? I love me a piece that has a question for the headline and doesn’t end up answering it. If you’re looking for concensus, start a poll. If you pose a question in the headline, answer it.

    • @Mike & Jeff

      PDO is supposed to indicate if a team is “lucky” or not … any value above 1000 would indicate “lucky” and any below “unlucky” … PDO includes the values of saves/total shots% and goals/total shots% …
      you have to follow the links to find out more … :)
      the idea of PDO comes from ice hockey.

      My opinion:
      PDO is still a very “green” stat, the implications have not been fleshed out at all and personally I would hesitate to use it other than novelty value … I wouldn’t draw any conclusions from it at this point in time.
      Further investigation is being done into the stat … some of the better teams have a constant PDO of 1020 for example … either they are always lucky or there is some element of talent in shooting and saving. So their PDO would never regress to 1000, but to 1020 … i.e. just showing a PDO number doesn’t tell you what a team’s natural regression state is.
      In the above example … I can’t tell what Liverpool’s PDO has been over the past 15 seasons say, so I can’t tell if a PDO for Liverpool of 1018 means that they are slightly “lucky” or that they are bang on their natural state.

      Also … the above graph screws with the data, as is shows TOTAL PDO and AVERAGE TSR!!! AVERAGE PDO would be a better comparison (or TOTAL TSR … depending on what you want to show). :)

      cheers.

      • Thanks for answering?

        • no worries. :)

          @Mike & Jeff

          I forgot to add that PDO should only be calculated for 11v11 situations on the field. Thus from the moment there is a red calculations should stop as an “unfair” situation has arisen.
          e.g. In their first game this season Liverpool lost away at WBA, during the match Agger got a red card, so PDO should be calculated up till that minute.

          That’s why PDO is a “green” stat … so much is still not figured out … what are the effects of a 10v11, 10v10, 9v10 etc. situation on it?
          Over a season the number of total minutes for such situations is fairly small so we need data from a whole series of seasons to see what happens and how to adjust PDO for such game situations.

          cheers.

          • Sorry but this is incorrect. PDO is just sh% + sv%. Maybe conversion rates are altered by 10v11 situations, but that would astonish me.

        • yes … sh% and sv% in normal situations i.e. 11v11 … you cannot just change a situation and assume that the “luck” factor still applies in the same way.

          Look at how ice hockey does it … PDO is only for 5v5 situations (actually 6v6, but they do not count the goaltender in ice hockey lingo) … as soon as there is a powerplay situation the PDO does not count anymore … granted powerplay situations are more extreme in ice hockey, where normally for extended periods the team with a man down is held within their own defensive area behind the blueline … this is not the case in football.
          Anyway, if there were in anyway benefits for playing with a man down in football, I am sure more teams would go about doing so.

          Now if football stats people have not taken this into account then maybe they should look into it … you cannot just “assume” something without doing any research on it … James Grayson has an excellent site and started looking into PDO for football applications … I am sure that he can devote a post on this subject.
          Let me put it this way … (from the very few examples I have gathered) yes, PDO is affected by a red card, but I cannot be sure as I do not have a ton of data to work with. I only follow one team’s stats …

          cheers.

          ps – please change the graph (also in the new post on Liverpool) to show average PDO, it would fit better with average TSR.

          • I link to Grayson’s work pretty much everytime I do one of these. Including in this post I believe.

          • yes I know, that’s why I mention it (I also read it, along with 11tegen11, de Volkskrant voetbal blog, etc.) … you’ve also set up a forum with him (or a forum was set up based on your ideas) … i.e. you have contact with him … i.e. you might suggest this to him … (he doesn’t post much, I don’t have twitter and am not a member of the forum so …)

            heh … only came to the Score to check out the excellent Drunk Jays Fans blog … figured I’d do my monthly check of Bandini/Horncastle blogs and I end up getting sucked into a discussion here … ah well.

            cheers.

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