Managers don't matter. Just ask the best manager in the world.
"I will tell you a secret," Pep Guardiola said in October. "The main thing is the quality of the players." He went on: "I try to figure out things, but at the end the players ... the success we had is because we have top players. This is the secret, no more than that."
Now, "managers don't matter" is a bit of a rhetorical overstatement. Manchester City wouldn't have won as many points last season if you were managing the team. Meanwhile, Chelsea probably wouldn't have finished higher in the table had they given you the reins rather than Frank Lampard after firing Graham Potter. Rather, what Guardiola is suggesting is that talent is the main driver of team success. Framed another way, player skill overwhelmingly decides what wins games. In fact, the authors of the book "The Numbers Game" found that player skill (as represented by wages paid) accounts for 70% of team performance. Somewhere in that remaining 30% sits the effect of the manager, along with other factors like, say, the random, and flummoxing bounce of the ball.
Managers do matter -- just way less than we think. And the limited impact makes that impact even harder to measure. In a league without a salary cap, and with massive team-to-team financial inequality and vastly differing team-building ideals, we can't just look at where a team finished and say, "The best manager finished first, the worst manager finished 20th."
Instead, we have to try to control for all of the other factors that influence winning. We can't do that with anything resembling precision because of all of the unknown factors that influence winning -- for example, is a player great because he's inherently great or because the manager deployed him in a way that made him great? -- so we're going to try a slightly different exercise.
And so, I've ranked and tiered all 20 Premier League managers by how confident I'd be that they would improve the 10th-richest team in the Premier League.