Attempting to generate some sort of evidence based explanation for why Manchester United have the 14th best defence in the Premier League on expected goals concede [THREAD]

We don't have good, publicly available defensive metrics. That may change in the future with tracking data, but, for now, all we have is our eyes. However, the issue with the eye test is that human memories are fallible: we all have biases, and as a result we...

remember certain events that fall in line with our own version of how events transpired better than events that fall out of line with said narrative. We know this about people, and I myself am no exception.

So, with that in mind, I decided the only good way to discern why United's defence is leaky this year compared to last would be to go back and watch every big chance and goal conceded by the club in the league this year and assign blame.

Why this approach is good: I was able to watch everything consecutively, pause and rewatch, and to take time to question my own interpretation of events. I even asked for second opinions on a fair number of the more complicated cases.

Why this approach is flawed: No two defensive breakdowns are the same in magnitude, and rarely is a defensive breakdown the fault of one player. As a result, attributing partial blame to multiple players for chances conceded of different quality is flawed.

However, it's better than what we otherwise have. So, with all that in mind, let's get to it

I've broken down defensive mistakes into the following categories:
- Duels
- Positioning
- Communication
- Turnovers
- Fouls
- Pressure/Tracking

Note the difference between a positioning and a tracking mistake: a positioning mistake is one where the defender is so out of position that they cannot recover, a pressure/tracking mistake is one where they are out of position but could recover and do not

Note, also, that goalkeeping mistakes are excluded. I did not endeavor to assess David De Gea nor Dean Henderson's performance this season, but rather the structural issues that saw them called into action. Dean Henderson did make 1 turnover leading directly to a goal.

LUKE SHAW:
6.2 Nineties Played

0.36 Mistakes leading to goals [p90]
+
0.48 Mistakes leading to chances
=
0.83 Total mistakes

0.00 Duel errors
0.60 positional errors
0.00 communication errors
0.12 turnovers
0.00 fouls
0.12 pressure/tracking errors

ALEX TELLES:
4.3 Nineties Played

0.23 Mistakes leading to goals [p90]
+
1.64 Mistakes leading to chances
=
1.88 Total mistakes

0.70 Duel errors
0.70 positional errors
0.00 communication errors
0.00 turnovers
0.00 fouls
0.47 pressure/tracking errors

HARRY MAGUIRE:
13.0 Nineties Played

0.15 Mistakes leading to goals [p90]
+
0.31 Mistakes leading to chances
=
0.46 Total mistakes

0.08 Duel errors
0.31 positional errors
0.00 communication errors
0.08 turnovers
0.00 fouls
0.00 pressure/tracking errors

ERIC BAILLY:
1.1 Nineties Played

2.76 Mistakes leading to goals [p90]
+
0.00 Mistakes leading to chances
=
2.76 Total Mistakes

0.92 Duel errors
0.92 positional errors
0.00 communication errors
0.92 turnovers
0.00 fouls
0.00 pressure/tracking errors

VICTOR LINDELÖF:
12.0 Nineties Played

0.58 Mistakes leading to goals [p90]
+
0.67 Mistakes leading to chances
=
1.25 Total Mistakes

0.75 Duel errors
0.42 positional errors
0.00 communication errors
0.00 turnovers
0.08 fouls
0.00 pressure/tracking errors

AARON WAN-BISSAKA:
12.0 Nineties Played

0.50 Mistakes leading to goals [p90]
+
1.25 Mistakes leading to chances
=
1.75 Total Mistakes

0.33 Duel errors
0.67 positional errors
0.42 communication errors
0.08 turnovers
0.00 fouls
0.25 pressure/tracking errors

TIMOTHY FOSU-MENSAH made one duel mistake in the first match week, but has not played enough to qualify.

SCOTT MCTOMINAY:
8.5 Nineties Played

0.12 Mistakes leading to goals [p90]
+
1.76 Mistakes leading to chances
=
1.88 Total Mistakes

0.35 Duel errors
0.47 positional errors
0.35 communication errors
0.12 turnovers
0.00 fouls
0.59 pressure/tracking errors

FRED:
8.1 Nineties Played

0.12 Mistakes leading to goals [p90]
+
1.96 Mistakes leading to chances
=
2.09 Total Mistakes

0.25 Duel errors
1.11 positional errors
0.00 communication errors
0.25 turnovers
0.12 fouls
0.37 pressure/tracking errors

PAUL POGBA:
7.2 Nineties Played

0.70 Mistakes leading to goals [p90]
+
0.84 Mistakes leading to chances
=
1.54 Total Mistakes

0.28 Duel errors
0.28 positional errors
0.00 communication errors
0.00 turnovers
0.28 fouls
0.70 pressure/tracking errors

NEMANJA MATIC:
4.8 Nineties Played

0.21 Mistakes leading to goals [p90]
+
0.83 Mistakes leading to chances
=
1.03 Total Mistakes

0.62 Duel errors
0.62 positional errors
0.00 communication errors
0.00 turnovers
0.00 fouls
0.21 pressure/tracking errors

DONNY VAN DE BEEK:
2.9 Nineties Played

0.35 Mistakes leading to goals [p90]
+
0.00 Mistakes leading to chances
=
0.35 Total Mistakes

0.00 Duel errors
0.35 positional errors
0.00 communication errors
0.00 turnovers
0.00 fouls
0.00 pressure/tracking errors

BRUNO FERNANDES:
11.5 Nineties Played

0.17 Mistakes leading to goals [p90]
+
0.26 Mistakes leading to chances
=
0.44 Total Mistakes

0.00 Duel errors
0.09 positional errors
0.00 communication errors
0.00 turnovers
0.09 fouls
0.17 pressure/tracking errors

JUAN MATA:
3.7 Nineties Played

0.00 Mistakes leading to goals [p90]
+
0.27 Mistakes leading to chances
=
0.27 Total Mistakes

0.00 Duel errors
0.00 positional errors
0.00 communication errors
0.00 turnovers
0.00 fouls
0.27 pressure/tracking errors

MASON GREENWOOD:
6.2 Nineties Played

0.16 Mistakes leading to goals [p90]
+
0.81 Mistakes leading to chances
=
0.97 Total Mistakes

0.16 Duel errors
0.16 positional errors
0.00 communication errors
0.16 turnovers
0.00 fouls
0.48 pressure/tracking errors

ANTHONY MARTIAL:
7.0 Nineties Played

0.14 Mistakes leading to goals [p90]
+
0.00 Mistakes leading to chances
=
0.14 Total Mistakes

0.14 Duel errors
0.00 positional errors
0.00 communication errors
0.00 turnovers
0.00 fouls
0.00 pressure/tracking errors

EDINSON CAVANI:
2.2 Nineties Played and no mistakes leading to chances or goals

MARCUS RASHFORD:
12.1 Nineties Played

0.25 Mistakes leading to goals [p90]
+
0.49 Mistakes leading to chances
=
0.74 Total Mistakes

0.08 Duel errors
0.00 positional errors
0.00 communication errors
0.08 turnovers
0.00 fouls
0.58 pressure/tracking errors

DANIEL JAMES:
In 3.0 nineties played has no mistakes leading to goals or chances

End of the part of the thread that's just statistics

I'm going to add some analysis later but Ill leave you with this for now: the further back in defence a player was, the more likely that a 'mistake' was highly consequential. It's also worth nothing that pressure/tracking mistakes for forwards and fullbacks are partially tactical

And if you really think I did all this work to forward an agenda: I was upset and surprised to see two of my favorite players in Aaron Wan-Bissaka and Fred show up so poorly here. More on that later.