"We've got to think about achieving success. Thinking about the good things, rather than thinking about what could happen."

Sarri has questioned his players' mentality repeatedly this season and ensuring there is no repeat of the Etihad debacle "starts in the mind", Barkley said.

Sarri's possession-based style of play and 4-3-3 formation, plus his unwillingness to try a different approach, have attracted scrutiny and criticism, including from Chelsea supporters.

But Barkley reckons, with time, Chelsea can fulfil their ambitions of a beautiful and successful game.

Whether Sarri has time, only Roman Abramovich knows and the Chelsea owner is not renowned for his patience.

Pep Guardiola's first season at Manchester City has been repeatedly used as an example of how patience can be rewarded.

But Guardiola had pedigree from Barcelona and Bayern Munich; former Empoli and Napoli boss Sarri is yet to win a trophy.

Barkley said: "We've got ambition to be one of the best footballing sides in the world. We're one of the biggest clubs in the world.

"The style of play the manager wants to play it's not where it's at right now. Over time it will come.

"He (Sarri) tries to improve every player. Throughout his career, you can see at Napoli how well he did with the players he had, how well he improved them.

"You can see on the training pitch a lot of things improving in each individual.

"We went through a bit of an up and down spell in the last couple of weeks, but we're confident we'll come through it and achieve success."

The midfielder has more reason than most to believe in Sarri and his methods.

The 25-year-old signed from Everton in January 2018, but arrived following a long-term injury and was a peripheral figure last term as Chelsea won the FA Cup in Antonio Conte's final match as boss.

Barkley has been more central this term, often starting big matches in Sarri's favoured three-man midfield and earning an England recall.

Barkley was an unused substitute in last May's FA Cup final, when Chelsea beat Manchester United 1-0 courtesy of Eden Hazard's penalty.

His desire for silverware was behind his move to Stamford Bridge and the Wembley win whetted his appetite.

"Last season I didn't really play much of a part in winning the trophy, so I see Sunday as the chance to win my first trophy at the club," Barkley said.

"Over the years – me, not being at the club – you see managers come, managers go. It's all about success at the club, winning trophies.

"That's why I came to the club and all of the players come to the club. If things aren't going well there's always going to be pressure that comes with it."

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