Jack Grealish is ready to be "the X factor" for Manchester City in their Champions League semi-final tie with Real Madrid, according to the club's former defender Kolo Toure.

Toure heralded the winger’s uniqueness and bravery with the ball ahead of what many have identified as treble-chasing City’s toughest challenge so far this season. 

Pep Guardiola’s men will be desperate to make it past Los Blancos after their opponents’ stunning comeback against his side in last year’s semi-finals.  

Pundits and fans have been identifying Erling Haaland as City’s key difference maker following a record-breaking first season in Manchester that has seen him score 51 goals in all competitions.  

But Toure feels it may well be Grealish who City end up relying on as they look to finally get their hands on the elusive Champions League trophy, with the first leg of their last-four tie taking place on Tuesday.

"He is such an effective player and for me it is unique players like that who win the Champions League because he has that X factor," Toure told Stats Perform about Grealish ahead of the match at Santiago Bernabeu.

"It is his personality. He's not scared, he likes getting the ball under big pressure, and they need him in the Champions League.

"I think he's going to be really big for them in the Champions League games coming up."

Grealish will not need reminding of last season’s disappointment in Madrid, where City led by two goals going into the final minute of the second leg before collapsing to a 6-5 aggregate defeat after extra time.

As City sought to put the tie beyond doubt, the Englishman was centre stage. He saw an effort cleared off the line by Ferland Mendy before the exceptional Thibaut Courtois saved from him as opportunities went begging.

Many questioned whether City had made the right move bringing Grealish to the club. A low output – just three Premier League goals and three assists – in his first season under Guardiola and a £100 million transfer fee did not help his case.  

He entered a squad stacked with attacking players who have technical ability in abundance and were already established as greats of the Guardiola era. The records of Bernardo Silva, Riyad Mahrez and Kevin De Bruyne speak for themselves.  

But Grealish’s development this season has been impressive, and this has not been lost on Toure. 

"I think when he came to City, he came to a different team," explained Toure.

"With Aston Villa, he used to play as a free man and he used to be the playmaker. He used to be the one who does everything when they have the ball. 

"They were working for him to make sure he just created chances on his own really by dribbling past one or two players and then passing the ball to his team-mates or scoring himself, and he had a habit of doing that from a young age.

"And then he came to Man City, which is a team with tactical discipline, which is a team with top players around him, which is a team that is not about one player but is about all the squad, it is about all the players on the pitch.

"And you find it difficult because he was learning the Man City way. 

"He was trying to be disciplined because when you have been a free man running everywhere and then your manager says ‘you just stay there and the ball will get to you’ [it is an adjustment]. When the ball doesn't come for 20 seconds, you just want to get it. 

"But Pep knew that this boy has big quality, and you just needed to be taught the tactical discipline and you can see how effective he is now.

"What happens when you have tactical discipline, you are not running everywhere on the pitch and you save a lot of energy and, when the ball gets there, you have plenty of energy to do even better than you used to. 

"And you can see how defensively he is working harder because he is not wasting energy. He is just in the right position for the ball get to him and then to attack one, two or three players."

Toure’s observations certainly stack up when looking at Grealish’s numbers. The England man has improved his assist output (11 in all competitions) and receives more progressive passes per game than in his first season at City, pointing to his better understanding of the manager’s demands in tandem with his team-mates.  

Guardiola is known to demand so much of his players and even Sergio Aguero once faced questions over his suitability. Many goals and many trophies later and that sentiment is one those who shared it will be hoping to forget. 

Throw in names like Mahrez and Raheem Sterling and the list of attackers who have taken time before growing into key roles at the club is now a who’s-who of City successes.  

Grealish will be hoping his critics will be quieter still as the season draws to a close following his breakout year at the top of English football.

But he along with his team-mates know Champions League glory will be the true marker of how they are viewed as City return to Madrid looking to show their growth and seeking redemption.