A look at 13.4 years of the Premiership. Part I: The mainstays

This is the first of a multiple part series in which I’m going to take a look back at the evolution of the Premiership since the turn of the century. As the following plots get pretty busy once a threshold of teams is passed I’ve broken down the teams into groups that I think will be interesting to compare. This time I’m looking at the seven teams who’ve been in the Premiership since its inception.

Depending on your browser these plots may look a bit squashed so I very much encourage you to click on these images to see the full screen versions in all their glory. There’s tons of cool little details in these plots – and there’s no way I’ll spot them all – so feel free to highlight anything I’ve overlooked in the comments.

Points

So let’s dig in. First, here’s the 38 game moving average of points scored by the seven Premiership mainstays since the beginning of the ’00-01 season. The points are plotted at the end of the 38 game period, so a point vertically above ‘1’ on the x-axis represents games 1-38 in the ’00-01 season, whilst a point vertically above the midpoint between ‘1’ and ‘2’ on the x axis will represent games 20-38 in ‘the ’00-01 season and games 1-19 in the ’01-02 season.

Mainstays points

The first thing that jumps out at me is that the Chelsea side of ’04-05 and ’05-06 was immense. At one point they had a 38 game run where they picked up 102 points (32 wins, 6 draws, 0 defeats), even United have never surpassed 97, and Arsenal are the only other team to have passed 90.

Also – teams can put in extreme performances over 38 games but that doesn’t always matter as it isn’t necessarily the ‘right’ 38 games (i.e., numbers 1-38 of a given season). Take Liverpool for example. At the beginning of ’06-07, and towards the end of both ’01-02 and ’08-09 they’re up there, if not ahead of everyone else, in terms of points scored over the past 38 games, but they never quite manage to maintain it until the end of a season. Villa are another perfect example of this – check out their 29 point run mid-way through the ’12-13 season. The dramatic drop-off at the end of the ’11-12 season was well compensated for at the back-end of ’12-13, but they were in real trouble for a while there.

Finally, with the exception of United, every one of these teams has had a span of 38 games where they’ve recorded 60 or fewer points and given how much time Spurs, Everton, and Villa have spent in the 30-60 point band it’s kind of amazing that none of them have been relegated.

TSR

Next I’m going to look at the same teams but through the lens of a metric called TSR, or total shots ratio. Put simply, it’s a measure of the proportion of shots taken by a team in its matches. Given its inate simplicity it’s a deceptively useful tool if we want to look at which teams are over- or under-performing at a given point in time, and is a frankly remarkable predictor of how teams will perform in the future. The average TSR of a Premiership winning side is 0.627 (i.e., for every 8 shots taken in their matches, the Champions would have taken ~5).

Mainstays - TSR

The first thing I want to note is just how damn good Liverpool were by this measure under Benitez from ’05-06-’08-09. There may have been flaws in Liverpool’s game but he gave them a damn good shot at winning the title throughout that span.

Next up is that dip from Villa mid-way through the ’12-13 season. It overlays perfectly with the lack of points scored during that period. As soon as they began to get dominated in terms of the shots that were taken the number of points they scored fell off a cliff.

With one blip during some meaningless games at the end of the ’05-06 season United were a constant .600 team or better for over five years. That’s really quite an incredible feat. Matching them have been Arsenal, who’ve been a truly dominant shots team since ’00-01 (and probably unlucky to only have two titles to their name over that period).

Spurs’ rise from irrelevance to the top tier has come in two bursts. The first was under Martin Jol in the ’04-05 season, and the second under a combination of Redknapp and AVB since the beginning of the ’11-12 campaign.

Finally, Chelsea were incredible under Mourinho, dropped off horrendously under Grant (which should have been a red flag for both Portsmouth and West Ham), began a recovery under Scolari, and finally peaked as a once-more excellent team under Hiddink. They remained a damn good team under AVB, and fell off a cliff when RdM took over. Right now they’re on the up, and once more belong in the top four.

PDO

Lastly I’m going to take a look at these sides by PDO. PDO is a nameless metric, created by Brian King, that is simply the sum of a team shooting percentage (goals/shots on target) and its save percentage (saves/shots on target against), and gives an average value of 1000. The reason that it is worth our attention is that it regresses heavily towards the mean, and has a large luck component over the course of a season. For reference, a crude estimate suggests 50 points of PDO is worth about 10 goals, or 4-7 points, over the course of a whole season, about half of which we’d attribute to luck.

Mainstays - PDO

There are tons of things to take from this plot.

The first is that these teams, as a group, have outperformed a league average PDO. This is important – and something I have an entire post dedicated to in the near future.

PDO probably cost Arsenal a great chance at winning the title in ’00-01. Had they saved shots at a league average rate they’d have been 9 goals better off. They finished 10 points behind United in the title race.

As I highlighted at the time, United were riding their percentages throughout the ’11-12 season, and City were favourites to catch them. That it came down to basically the last kick of the season is pretty amazing really. United were at it again last season, winning the title thanks to a gaudy 1120 PDO. So far in ’13-14 their PDO has regressed >60% of the way towards the mean of 1000, at 1045 after 16 games, and is part of the reason they find themselves out of the top four.

If we overlay this plot on the TSR one above we’d see that, despite going through a prolonged period where they posted an unprecendented TSR, Liverpool never really had a full season where the percentages broke their way. Maybe that’s an inherent part of Benitez’s coaching style, maybe Torres et al. weren’t great finishers, maybe Reina in his prime wasn’t all he was cracked up to be, maybe it’s all of those. Either way they were dominating territory at an almost unprecedented level, and, as I said above, can probably regard themselves as unlucky not to have picked up a single title over that span.

That’s it for this part. If you’ve spotted anything interesting I’ve missed feel free to post below. Next time I’ll come back and look at the teams that spent significant periods in the league, and I’ll also come back and look more closely at the PDO of these teams over multiple seasons.

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