King played 11 games without a goal for Everton last season but was in devastating form on his return to Goodison Park where Watford scored four times in the last 12 minutes to come from behind against Rafael Benitez’s men and record their first victory at the famous old ground.
Everton had looked to be on for the victory after Richarlison came off the bench to head them 2-1 up in the 63rd minute but after Juraj Kucka headed Watford level, King struck twice before Emmanuel Dennis added a final flourish.
King’s first had come 13 minutes in to cancel out an early Tom Davies strike.
It was a stunning finish to the match, all the more so given Ranieri’s men were humbled 5-0 by Liverpool just a week ago in the Italian’s first game in charge.
But while they celebrated what they will hope is the start of a turnaround to their fortunes, Ranieri’s old friend Benitez was left to ponder a second consecutive home defeat and their ninth of 2021 – one shy of the club’s record in a calendar year.
The early signs had been good for the hosts.
With Richarlison deemed fit enough only for the bench after six weeks out with a knee injury, Benitez made two changes to the side beaten 1-0 at home by West Ham last week and both players to come in – Davies and Anthony Gordon – were involved as they struck just three minutes in.
Benitez had said he needed to find someone with the right energy to replace the injured Abdoulaye Doucoure and it soon became apparent why Gordon got the nod as he drove Everton forward, playing in Demarai Gray whose low cross was turned in by Davies for his first goal of the season.
But a set-piece offered Watford a route back into the game as Craig Cathcart flicked on Ozan Tufan’s free-kick for King to turn in at the far post and though the flag initially went up for offside, VAR would overturn the decision and level the scores.
Encouraged, Watford continued to create chances – Moussa Sissoko drilled a shot wide from the edge of the area after good link-up from Adam Masina and Cucho Hernandez, with the latter then seeing a bending shot deflected narrowly wide.
Richarlison was sent out to warm up as the second half got under way, with Everton seeking a spark as Watford threatened again – Jordan Pickford making a superb save to deny King at close range.
Benitez responded by sending on Richarlison on the hour mark but his decision to replace Gordon was greeted with boos from the stands.
They turned to cheers three minutes later, however, as Richarlison beat Ben Foster to Michael Keane’s ball to head into an open net.
Watford responded well. Kucka drew a good save from Pickford with a shot from the edge of the area before some calamitous defending almost gifted openings to King and substitute Joao Pedro.
They were warnings which went unheeded. Kucka headed level from Hernandez’s corner and then two minutes later Watford hit Everton on the break as Dennis played in King to fire beyond Pickford.
Having lost their lead, Everton lost their way entirely.
Terrible defending saw them pass up opportunities to clear the ball before it fell for King to finish his hat-trick in the 86th minute.
As the home fans streamed for the exits, Dennis added an exclamation mark in stoppage time.