What's with Everton's home form?

This weekend Everton failed to win at Goodison Park for the eighth time in nine league matches. When asked about his side's home form, manager Roberto Martinez had this to say:

"Clearly the psychological aspect of going into a game is not right at the moment. We feel we can let our fans down, that we’ve got something to lose…the doubts, the communication is not what it should be. And that’s something that’s affecting our scorelines."

Watching the game on Saturday, one would tend to agree with Martinez's assessment. The team looked totally disjointed, with fingers being pointed and nervy moments aplenty. The pressing was sporadic and disorganized, the passing lacked ambition, and the defending was desperate.

Without a doubt, the home results are a cause for concern. At the moment, Everton are tied for second-fewest points accumulated at home, and they have conceded more goals at home than any other team in the division. Over the last 15 Premier League seasons, 25 sides have had an equal or worse home record than Everton's current clip; 19 were relegated. None finished higher than 14th.

Where has it gone wrong for the Toffees at Goodison? Looking very quickly at the table, we see that scoring at home has generally not been an issue. Rather, it's the defense that has been especially susceptible to conceding (1.75 goals against per game at home versus 1.00 away).

Looking a bit more closely, one thing that jumped out at me was Everton's defensive record away from home in the first half of games:

(data is per game for league matches)

They appear to be doing a better job in away matches at tightening up out of the gates. Whether that's by luck or by design is unclear to me, but most teams tend to take a more conservative approach on the road and perhaps in the case of Everton it's actually worked this season. It also lends itself to the narrative that away from home they've been more able to grow into games. On the flip side, conceding a goal in the first half of every game you play in front of your own supporters cannot be good for the nerves. Nothing turns an atmosphere toxic like an early goal for the away team--Danny Welbeck's 7th minute tally on Saturday of course being the freshest example in the memory.

With that being said, goals often do not tell the story of the performance, and indeed there is an alternative account to be spun here:

(data is per game for league matches; expected goals are according to Michael Caley's model)

On first impression, the "Everton are crap at Goodison" narrative doesn't hold sway. Looking at these numbers alone, you'd probably say that this is a half decent side. Sure, they could stand to concede fewer shots, but the attacking output is good enough to cover for it.

Simple possession and passing metrics tell roughly the same story as the shot numbers:

(data is per game for league matches)

On average, Everton are shooting more, conceding fewer shots, creating roughly the same quality of chances, conceding fewer quality chances, possessing the ball more, passing the ball more, and spending more time in the opponent's end of the pitch when they are at Goodison compared to when they are on the road. Yet according to the table, the Toffees are a relegation-caliber team at home.

So what gives? Recall what I noted above, that conceding goals rather than scoring them was the main difference between Everton's home and away form in the league table. But if shots conceded and expected goals conceded still favor the home column, then something else must be going on.

This is where save percentage enters the conversation. As a reminder, extreme save and shooting percentages usually indicate that a team is strongly affected by luck.*

16 percentage points is an enormous swing, in this case potentially enough to take a top 10 TSR team at home and effectively turn them into Sunderland. Indeed only Liverpool have a more drastic home/away PDO differential--one wonders if there's something in the Merseyside water that's causing the hometown heroes to be so unlucky.

Before you run away with that storyline though, remember that Everton are still at an almost league average PDO at home, as their high shooting percentage offsets the low save percentage. So on the macro level it appears that overall Everton aren't unlucky at home, it's just that their positive skews away from home make it seem like they're a better team than they are. But given their shot numbers, I'd argue that their low save percentage is hurting them more than their high shooting percentage is helping them at this point. They already concede a lot of shots on target; to have them be hitting the back of the net at one of the highest rates in the league is devastating.

In short, Everton haven't been that terrible at home this season. I wouldn't go so far as to call it a "one-off" but in truth prior to Saturday Everton hadn't been so badly outplayed at home in the league since perhaps the Manchester United game way back in October. We also shouldn't forget that the Toffees have 4 wins out of 4 in cup ties at Goodison this season. If the manager does get the sack this summer, it shouldn't be because the team isn't good enough at home, but because they're not good enough...in general.

With that being said, getting bad results at Goodison is becoming a bit of a habit for Martinez. Everton's 28 home points last year was their worst in nine seasons. Even if it is being swayed by factors that are perhaps out of the manager's control, and even if home field advantage isn't really a thing anymore in the Premier League, poor home form is always a tough pill to swallow for the supporters who pay their hard-earned money to come to the ground. While Martinez might feel justified in asking for patience, it's little surprise that many fans are losing theirs.

*In addition to the James Grayson link, this is probably the simplest explanation I've read of why shooting percentage, save percentage, and PDO is useful.