"We cannot replace him," Pep Guardiola insisted on the eve of Sergio Aguero's final game in a Manchester City shirt.
Four years on, do City find their fortunes tied once again to the fitness and form of a lethal striker with unique attributes and singular talent?
"Without him, it would be tough to be honest," Guardiola admitted after Erling Haaland's magnificent first-half double helped City leapfrog Bournemouth with a 3-1 win on Sunday.
Not everyone can boast a goalscorer of Haaland's quality, but each Premier League team has that one player they cannot do without - be it for their leadership, playmaking, or game-changing flair.
From the "soul of the team" to an "absolute warrior", here are the Premier League's 20 key players, as chosen by our fan writers.