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Analyzing Chelsea’s game-state and goal-timing data under Antonio Conte

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‘When’ in matches are Chelsea underperforming compared to last season?

Chelsea v Crystal Palace - Premier League Photo by Catherine Ivill/Getty Images

So here we are, with 8 league matches to play, including two heavyweight bouts with Spurs and Pool. Literally all of the marbles are at stake, as Chelsea are currently on the outside and looking in, but hopeful of taking the place of either of these two clubs. Needless to say, course corrections and adjustments are due, and some inspired play is in dire need.

I’ve been looking at some data, on how we are playing this year versus how we played last year. Trying to find patterns, as I always am. In the past, I’ve talked about our poor conversion rates, and our lack of goals from different individuals at different times, as well as lots of different perspectives to try to figure things out. Today I want to look at two specifically, that tend to drive the same course:

  1. The State of the Match
  2. The Timing of the Match

I’m hopeful that these will glean some insight on how we’ve been, and where we might improve during this final run. Lest we not forget, 8 matches is 21% of the season, and while at times it hasn’t looked very hopeful, that’s an immense amount of season left with which to unwind our knot of a season and wander true.

THE STATE OF THE MATCH

What this means, in generic terms, and for this analysis, is our score relevant to our opponents during the match. There are five possible options:

  • Goal Differential > +1
  • Goal Differential +1
  • Goal Differential 0
  • Goal Differential -1
  • Goal Differential < -1

In essence, do we have more than one goal than our opponent, one goal more, an even score, one goal less, or is our deficit more than one goal, respectively.

These states of the match will often have an impact on how we are playing at any given point. If we are behind, we are playing poorly and the numbers would reflect this. Similarly if we are more than one goal ahead, we might ease up a bit, and not press as hard as we would if the match was perhaps at a draw. I have data, accessed from the site understat.com, that breaks this information out, for both this season and last season, listed below. I’ve highlighted a few key points of data that I thought merited discussion.

Obviously in both seasons, we spent the majority of our time in a state of no goal differential. This is how matches start, and often how a good portion of matches stay, for at least some duration.

Key Points

  • We spent almost a quarter of our time last year with a one goal lead. And 42.8% of our time in the lead, in general. This season? Not so much. Only 17.1% with a one goal lead, and only 36.4% (just barely more than one third of the time) with the lead. We know we’ve had trouble scoring goals, and this definitely shows what an impact that’s had.
  • What’s really bizarre, is that we spent 4.3% of the time last year down more than one goal, yet won the league. And this year, in just 21 minutes we basically gave up the season with losses to Bournemouth and Watford, and I think Burnley at the start. A club like ours should never be giving up 3+ goals, ESPECIALLY to the bottom half of the table. Want to know why Manchester United are in second place right now? It’s not because they score a lot of goals, because they don’t. It’s because they rarely give up a lot of goals, thus making it easier to win.
  • Look at how many goals we scored last season when either tied or up only one goal. Just over 75% of our goals were from that position. Scoring when tied is moving to a winning position, and scoring when up one is moving to a safer winning position. Those are important numbers. This season? Not only are we scoring less, but we are scoring less when we need to be as well. Hold the thought that we scored 63 goals last year when either tied or up one for just a moment, and notice this year it’s at 62.8%, a 13% drop. And now think about those 63 goals, because in the same situations this season, we’ve scored 32 goals. Basically half as many. Now, it is important to point out that we still have 20% of our matches to go, and the last season numbers are for the WHOLE season, but still. This is abysmal.
  • Lastly, I want to point out a horrific trend with respect to goals scored against us. Our biggest bucket with respect to goals against was when we had a one goal lead. Not ideal, and we definitely often pushed back into the lead, as we only lost five times last year and only drew three times, but notice this year. 13 goals is again our biggest bucket (with 20% to go!) but this time, it’s when tied. We are either losing, or falling behind. And we will revisit this a bit more in the next section, when we discuss match timing.

MATCH TIMING

When we think of Match Timing, what we mean is the different periods throughout the match. In the case of the data I have, from the same source, it’s the following time periods:

  • Minute 1 to Minute 15
  • Minute 16 to Minute 30
  • Minute 31 to Minute 45 (including stoppage)
  • Minute 46 to Minute 60
  • Minute 61 to Minute 75
  • Minute 76 to Minute 90 (including stoppage)

This gives us six even set periods of time, three per half. This also gives us a nice balance, as there is a start-of-half, middle-of-half, and end-of-half for each half. These are good splits.

I’ve done a lot of highlighting here, because I think there are some very important distinctions, which I list below:

  • We take a higher percentage of our shots in the first half now than we did last year, 46.4% to 43.6%. Not much of a difference, but we do take more.
  • We score the second most goals in that second split, which is a high number, and seems to be indicative of a counter attacking team, as I’ll show in a bit. We score a LOT less goals coming out of the half, though.
  • The first, third, fifth and sixth splits are all similar in terms of shots allowed, yet only those last three are similar in terms of goals allowed. It’s like we are really shored up defensively at the start, and then tend to fall apart those other times. I’m not surprised about the second split, that’s our strong one, and the split out of the half we should be fresher and better set defensively.
  • We used to rarely concede in that 61-75 split last year. Used to not give up shots, either. If I remember correctly, and it’s quite possible I’m not, we used to play a bit of possession around that time, and also tighten up defensively. Conceding 3 goals in 38 matches in that split is about as rock solid as it gets.

How do the other top clubs look? I wanted to see a bit of comparison, so I put together similar tables for 17-18 for the other four Top sides (sorry Arsenal, but you are a ‘bad’ this year, deal with it).

Besides Man City, the other three clubs all have slow starts as well, so nothing wrong with us there in my opinion.

  • City shut the door in that second split defensively
  • Liverpool are running teams ragged in that fifth split
  • Spurs out of the half, that’s incredible. Not only do they score the most goals then (14 in one split) but they have literally given up 0 goals in that time. Very impressive, little brothers to the North, very impressive.
  • Man United is like some sort of weird pattern, defensively. 4,2,5,4,2,4 in terms of goals given up. Oddly consistent. And they give up a LOT of shots, and it’s so consistent, 50, 62, 55, 61, 58, 66. Those are like test scores they are so similar. They should be thankful they have DDG to keep them afloat.
  • Man United do tend to score more towards the end of halves, but they also have a lot of attacking threat and likely catch teams tired.
  • Both City and Pool have their highest shooting and second highest scoring splits right out of the half. That tells me that coaches made good adjustments at half time. Spurs would be technically in this bucket too, but not to the overwhelming degree of the other two clubs.

CHELSEA ARE A BIT MORE AVERAGE THIS YEAR, IS WHAT I MEAN

At the end of the day, we have had too many bad matches defensively, and not nearly enough converted shots, as well know all too well. But now we know a bit more of that detail.

  • We know that we used to score a lot of goals from drawn and one-up positions, and while we are still doing that,it’s less often.
  • We know we are giving up way too many goals when tied
  • Those really bad matches (Bournemouth, Watford, Burnley) haunt us so much. Even just five points from those three would have put us even with Spurs, and potentially ahead of Pool.

What other thoughts do the rest of you have? Feel free to share in the comments section.