Victory for Pep Guardiola's side came a week after the Premier League trophy was retained to join the League Cup and Community Shield already in City's possession. "What a season," City captain Vincent Kompany said. "What a tremendous club."
But the unprecedented achievement by football's costliest squad comes against the backdrop of investigations into City's compliance into football's spending rules that could lead to the Abu Dhabi-owned team being banned from the Champions League.
More than $1 billion has been spent on transfer fees alone since 2008 when Sheikh Mansour bought a team that was more accustomed to playing in lower leagues than lifting trophies. It wasn't until 2011 that City ended a 35-year trophy drought by winning the FA Cup.
Now City is the undisputed power of English football — a status it claimed from neighbor Manchester United. "It's one of the best seasons I have experienced as a manager," said Guardiola, who won titles previously at Barcelona and Bayern Munich.
Watford was contesting its first cup final in 35 years and never had a look in after Roberto Pereyra was denied by goalkeeper Ederson of the chance to snatch a shock lead in the 11th minute. Not long after, Watford fans were made to endure City players celebrating in front of them.
After Abdoulaye Doucoure gave the ball away, City broke forward and Sterling headed through for David Silva to strike into the net. City's other Silva — Bernardo — was the provider of the second in the 38th, chipping to the far post where Gabriel Jesus diverted the ball into an empty net. Sterling ensured it crossed the line but his Brazilian teammate was credited with the goal.
The onslaught came in the second half with De Bruyne exerting his influence after coming off the bench. The Belgian netted in the 61st, receiving the ball from Gabriel Jesus, who had combined with Sterling.
Gabriel Jesus found the net seven minutes later after being released by De Bruyne's throughball, sliding past Heurelho Gomes after the goalkeeper came off his line. Then the record-equaling final victory margin came from a double inside six minutes from Sterling, who grew up near Wembley and has a tattoo of the stadium's arch.
The Football Writers' Association player of the year tapped in after latching onto Bernardo Silva's cross in the 81st, and met the rebound after Gomes pushed his initial shot onto the post. "It just shows what the manager's building here," Sterling said. "At the start of the season he said, 'Let's try and get the mentality right and go for the Premier League again,' and we've done that again, exceptionally well.
"It's a credit to all the boys, being mentally switched on throughout the season which has been long with the World Cup as well. Everyone's been focused and on their A game the whole way through."
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