The Argentine striker halted his own six-match drought without a goal as he fired in two fabulous first-half goals before Ilkay Gundogan added another brace to keep City on top of the Premier League.
It’s been a tough month for Aguero, who has missed two penalties — one for City and for Argentina — while he was dropped for the Champions League defeat to Barcelona in the Nou Camp.
It led to questions about his relationship with Guardiola with the City boss repeatedly emphasising he wanted more from the 28-year-old.
It seems to have worked with statistics showing that Aguero ran 2.4km more in the win at the Hawthorns than his average for last season and the City boss was delighted.
“Sergio’s so important for us,” Guardiola said. “We don’t have too many strikers. Brazilian Gabriel Jesus is going to join us in the summer and he will help us a lot. Kelechi is a young player - a huge talent but he is still learning.
“Sergio is a special player. We have to convince him how special player he is for us. We need him a lot. When he’s in that behaviour and has that hunger in that moment Sergio is decisive. He’s a big part of the history of this club and we want to help him to become a bigger part of this fantastic club.”
Aguero showed his quality with his two brilliant strikes. He opened the scoring in the 20th minute when he darted onto Gundogan’s through ball to smash the ball under Ben Foster.
His second was even better as he pounced on hesitancy in the Baggies to defence to smash a 20-yard strike into the top corner.
Guardiola believes that Aguero is as good as Barca’s holy trinity Lionel Messi, Luis Suarez and Neymar in the box and wants him to prove it when the City boss faces his old club on Tuesday.
“In the box, he is at that level,” Guardiola added after confirming he would start.
“He is one the nicest players I ever trained in my career. It is a pleasure for me to work with nice people and Sergio is one of the best ones by far, but to convince him he has to believe how good he is and how we need him.
“I am talking about he has to feel how important he is for us. When he is happy of course all the team is happy.”
Guardiola admitted his side needed a win to regain their confidence after a month without one and he will be delighted with the way they delivered.
City didn’t look too short of belief as they dominated the first half and could have gone in at half-time better than their two-goal lead.
West Brom improved after the break and Salomon Rondon miscued two half-chances to pull themselves back into the game. But Gundogan finally put the game to bed in the 79th minute when he sprang onto Aguero’s flick pass to add a third.
And there was still time for another when fit-again Kevin de Bruyne picked out the German international in the box to sweep in a fourth in the 89th minute.
Guardiola said he never doubted his attacking principles despite their troubling run of results.
“After six games without winning we needed that for the head,” he added. “The problem when you don’t win a game or lose a game is not the three points it’s that you miss a little bit of confidence for the next one.
“And that’s happened in that period because we played quite well but of course when you don’t win but your argument about how many good things you did sounds like excuses.
“When you win you are right and when you don’t win you look for excuses which is why it is so important to win the game.”
There was little to cheer Tony Pulis in a week when he signed a contract extension at the Hawthorns. He couldn’t even bring himself to face the press after the game and left it to assistant Steve Kemp to admit the Baggies had been second best.
“Sometimes you have to hold your hand up; if you’re playing a lesser team sometimes you get away with it - not against these,” Kemp said.
“Aguero’s two goals were tremendous. You know he’s a good player but you hope he’s off-colour a little bit. He wasn’t, and you find yourself in trouble.”
Foster 6, Dawson 6, McAuley 6, Olsson 5 (Leko 51, 7), Nyom 6, Evans 6, Chadli 6 (Robson-Kanu 87), Fletcher 5 (Morrison 51, 5), Brunt 6, McClean 6, Rondon 6.
Myhill, Gardner, Phillips, Galloway.
Bravo 6, Fernando 6, Stones 7, Otamendi 7, Kolarov 6, Gundogan 8, Fernandinho 7, Sterling 6 (Navas 77, 5), Silva 7 (Garcia 83), Nolito 6 (De Bruyne 68, 6), Aguero 9.
Caballero, Kompany, Clichy, Iheanacho.