Sept 20 (Reuters) - Manchester United ( MANU ) boss Ruben Amorim said not even the pope could make him deviate from playing with a back three despite mounting pressure following a dismal run, adding that abandoning his preferred formation would undermine him in his players' eyes.

Amorim took charge of United in November but guided them to just seven wins in 27 league matches and their worst-ever finish in the Premier League.

This season's start has also been far from convincing, with the Portuguese manager overseeing one win in four Premier League games and a shock League Cup exit to League Two (fourth-tier) side Grimsby.

He has used three centre backs throughout his tenure at United, despite the rest of the "Big Six" all opting to play a back four.

United co-owner Jim Ratcliffe visited the club's training ground on Thursday, and Amorim was later asked if the British billionaire had suggested altering the team's set-up.

"No, no, no... Not even the pope will change (this). This is my job. This is my responsibility. This is my life. So, I will not change that," Amorim told reporters on Friday ahead of United's home meeting with Chelsea.

"If I'm a player and I have a coach that, with a lot of pressure and (people) all around the world are saying, 'You need to change the system', says 'I'm going to change', they will look at me in a different way.

"Everything is important when you think about the impact that a decision is going to have on the team. I'm doing things my way. I hope to have the time to change, but it will be an evolution."

Amorim has also received criticism for his decision to play Bruno Fernandes in a deeper midfield role, despite the Portuguese international having previously been successful in a more attacking position.

"I want Bruno to have more possession to try to control the game," Amorim said.

"Maybe he doesn't have the same freedom to get inside the box but he is getting there and he can do his shots. Sometimes we miss Bruno in front a little bit, but if (Matheus) Cunha is there we have an extra player.

"I'm just trying to balance the team and imagine the game, and I see Bruno well. He's frustrated because he is not winning and sometimes he likes to go further. But he has a job to do."