LEICESTER CITY rocked world football to its core last season.
The reverberations are still being felt at Manchester United, Manchester City, Chelsea and Arsenal.
To strengthen their foundations, the silverware hunters who lost out to the Foxes are taking no chances.
Three of them have installed a managerial legend for the new campaign. The other is sticking by a man who, despite a barren spell by his own standards, has already carved his niche in history.
The records at club level of Pep Guardiola, Antonio Conte and Jose Mourinho – until last season – speak for themselves.
Arsene Wenger has had better years than season 2015/16.
The four, you would expect, will be battling between themselves for the Premier League crown.
And in a game now driven as much by money as success, qualification for the Champions League remains a qualify-or-else scenario.
Chelsea missed the UEFA gravy train by a mile last season and it cost Mourinho his job as early as December.
United and City scrapped for the fourth qualifying spot and City hung onto it on goal difference.
United allowed Louis van Gaal a week’s grace to win the FA Cup then dismissed him. Two years earlier, David Moyes was sacked the day after it became mathematically impossible to secure a Champions League place.
It’s now the established bottom line for United managers. If the playing field is level, Mourinho should also be dismissed at Old Trafford if he fails to make the top four.
Of course, executive vice-chairman Ed Woodward won’t want to announce another embarrassing misjudgement next May, so United are making sure that Mourinho almost can’t fail.
They are giving him the most-expensive player in the world in Paul Pogba, and one of the game’s true superstars, Zlatan Ibrahimovic.
Compare United’s current squad to the one Moyes inherited from Sir Alex Ferguson or the injury-ravaged group that Van Gaal had for much of last season.
If Mourinho can’t get these players into the Champions League, and at least challenging for the Premier League crown, his label as a serial winner will need serious revision.
Last season he lost his veneer of invincibility over four meltdown months. The question is whether that was a blip, or a deeper malaise.
Roman Abramovich always sacks his managers when Champions League participation is threatened.
He did it first time round with Mourinho and with Luis Felipe Scolari, Andre Villas-Boas and Roberto di Matteo.
In all those cases, the caretaker turned it around. Last year Chelsea were so far adrift when Mourinho left that the Russian wrote off the season and waited for Antonio Conte to become available.
But make no mistake, the Italian will have the same briefing as every other boss Abramovich has employed.
Conte arrived with a reputation for discipline. In charge of his country at the Euros, he gave everyone a glimpse of his passion with his instruction-screaming, ball-kicking, dug-out-climbing antics.
But Chelsea fans should be wary of rushing to judgement. Remember that United fans were gushing about Van Gaal’s genius when they watched their boss-to-be at the World Cup in Brazil.
Manchester City had pursued Pep Guardiola ever since his old Barcelona mates, Ferran Soriano and Txiki Begiristain, started running the club.
The announcement last January that he would be taking over from Manuel Pellegrini proved a distraction. Yet the Chilean still won the League Cup, reached the semi-finals of the Champions League and secured his top-four finish.
Guardiola is meant to be an upgrade on Pellegrini. So that level of success would be failure.
The Board can’t afford that, hence City becoming the first Premier League club to take their summer spending past £100m.
This is the first real test of Guardiola’s reputation as the world’s best coach.
At Barcelona, he won two Champions Leagues and three
La Ligas. But he was able to call on Lionel Messi every week.
At Munich, he won three Bundesliga titles and two cups but Bayern’s financial power means they can buy domestic trophies.
City have a lot of cash too, but not significantly more than their rivals. And they don’t have Messi.
Most pundits believe the big-name manager most likely to be squeezed out of the top four, and with it a lucrative Champions League place, is Arsene Wenger.
Mind you, we say that every year, and for 20 seasons on the trot he’s fulfilled his annual remit.
As usual, the Frenchman has been slow to spend and has been muttering darkly about the ridiculous size of fees swilling around.
The law of averages says he’ll miss the cut one year, and it would be ironic if it happens this season when his contract is due to expire.
It would be no surprise if this was Wenger’s last season at the Emirates.
Of more intrigue will be whether Mourinho, Guardiola or Conte will do enough during the campaign not to join him on the dole queue.