Despite the so-called "Catalanisation" of the club, with former Barcelona figures filling the manager, chief executive and director of football positions at the Etihad Stadium, Al Mubarak is the man who wields the real power at City, having been handpicked by owner Sheikh Mansour bin Zayed al Nahyan to run the club shortly after his takeover in 2008. When Al Mubarak talks, it carries weight, because he says what Sheikh Mansour thinks; his 2017 statement could be pretty brutal if his 2016 assessment, recapping Manuel Pellegrini's final year in charge, is anything to go by.

"I think all of us came with high expectations for this season," Al Mubarak said in June. "I think, at the end of the day, I cannot hide the disappointment of myself, obviously Sheikh Mansour, I know the fans of the club and I'm sure the entire team."

Just rewind to the end of last season and look at City's achievements under Pellegrini: The club won the League Cup, secured a top-four finish in the Premier League and reached the semifinals of the Champions League for the first time, narrowly losing 1-0 on aggregate to eventual winners Real Madrid. City failed to win the Premier League, but they won a trophy and almost made it to the Champions League final. By that point, however, they had already announced Guardiola was on his way to transform the club and elevate the team to a whole new level.

"I'm absolutely excited about Pep joining our team," Al Mubarak said in that same end-of-season review. "I consider Pep to be one of the best, if not the best, manager today in football. We are getting a manager who epitomises passion and commitment. He's a proven winner ... a passionate man, someone who I think will be an incredible asset to Manchester City.

"I have no doubt he will transform our team to a new level."

This is where it begins to get awkward for Guardiola. Exiting the Champions League in the round of 16 stage was not part of the script, certainly not for a coach who has never previously failed to reach the semifinals. Being knocked out by Monaco, a team built on youth and homegrown players, was definitely not what Sheikh Mansour and Al Mubarak expected when they proudly heralded Guardiola's arrival and handed him over £150 million for new signings.

But City are out of the running for the Premier League title and have seen Manchester United succeed them as League Cup winners in 2017. If they also fail to win the FA Cup, the nightmare scenario of finishing the season empty-handed will leave Al Mubarak to compose a very tricky end-of-term review.

Will he really tell Guardiola that this season simply has not been good enough?

By the standards with which Al Mubarak judged Pellegrini, Guardiola has already failed to measure up, but Manchester City are now all about the Spanish manager, and it's difficult to imagine the Abu Dhabi hierarchy criticising him in public. However, Guardiola should not be spared the scrutiny that his predecessor was exposed to, especially as the same failings of the Pellegrini regime have been repeated in this season's disastrous Champions League campaign.

Pellegrini was castigated for his tactical decisions and team selections in the Champions League, but Guardiola has been no better. His decision to drop Sergio Aguero against Barcelona in the Nou Camp in October backfired spectacularly, with the Spanish champions winning 4-0 against a toothless City. Meanwhile, he continues to pay for his decision to offload goalkeeper Joe Hart and replace him with Claudio Bravo, who has been so lacking in the ability to keep the ball out of the net that City supporters have cruelly nicknamed him "The Hologram."

Guardiola also overlooked long-standing weaknesses at full-back when adding a succession of attacking players to his squad and has failed to resolve the club's defensive shortcomings. It's true that he has made City a pleasure to watch and unearthed true stars of the future in Leroy Sane and Gabriel Jesus, but the best coaches should really make their players better, and Guardiola has not done enough of that.

But let's go back to the tactics and focus on why it went so wrong against Monaco.

Having seen his team fight back from 3-2 down in the first-leg to win 5-3, Guardiola should have travelled to Monte Carlo and simply shut the tie down. Forget about the beautiful game: Just get the result in stifling your opponent by defending a two-goal lead. But by selecting Fernandinho as his only defensive midfielder, Guardiola basically sent his team out with a 4-1-5 formation.

City were far too open and Monaco made them pay.

Guardiola's decision-making proved costly, as Man City were dumped out of Europe. It's something he must answer to.

Guardiola could perhaps play that way with his great Barcelona team or the supreme Bayern Munich outfit he took to three Champions League semifinals, but he cannot replicate that style with this City squad. And so they ended the night as the first team in Champions League history to be eliminated in a knockout tie after scoring five goals in the first leg, a rather dubious distinction.

Guardiola stubbornly refused to concede after the game that he was at fault for the defeat.

"At this level, you have to play more than 45 minutes," he said. "We just played for 45 minutes."

When asked what he will do now to be the man City thought they had hired by leading the club to Champions League glory, Guardiola simply suggested we can expect more of the same.

"I tried, and I will continue to try," he said. "If we had played like we played in the second half, it would have been enough. This competition is so demanding, but we are going to learn and come back better."

City will need to get better, but so must Guardiola. If not, he can expect to be told exactly that by his boss in Abu Dhabi this summer.