Sometimes you have to hear from the footballers who have been in Lionel Messi's direct line of vision to understand what it must be like, as an opposition defender, to see him advancing with the ball. Asier del Horno sums it up pretty well. "Aargh," says the former Athletic Bilbao, Chelsea and Valencia player. "Difficult, very difficult. The situation you're in, his divine inspiration. He drives the ball forward, quickly, with the ball glued to his foot. He has speed, he has skills … aargh, he's a real problem for any defender."

Antonio Conte, the Juventus coach, was asked if there was a way to stop Messi. "Only with a gun," he replied. Internet videos promise to reveal the secret then just reel off some of the worst chops and elbows and kicks against those multimillion-pound insured limbs. "Defenders need to keep a tight line, be aggressive and hold the position well," is Del Horno's verdict. But you have to catch him first and that is the first problem for Manchester City tomorrow. As Thierry Henry points out: "If he has a good day, there is really no way of stopping him."

Carlos Queiroz, Sir Alex Ferguson's assistant when Manchester United won the Champions League in 2008, was so obsessed with doing just that he used sit-up mats on the training pitch to prepare for the semi-final against Barcelona and show the players exactly where they had to go. "We'd never seen such attention to detail," Gary Neville recalls. "We rehearsed time and again, sometimes walking through the tactics slowly with the ball in our hands."

It went against everything Ferguson wanted in his teams – "defended really deep, put myself through torture, put the fans through hell," he writes in his latest autobiography – but United did not concede a goal over 180 minutes and went through thanks to a Paul Scholes special. Ferguson, sans Queiroz, then abandoned those tactics against Barcelona in the 2009 and 2011 finals. "I wanted a more positive outlook and we were beaten partly because of the change in emphasis. If we had retreated to our box and kept the defending tight, we might have achieved the results we craved."

The disparity is worth noting because, if there has been one common theme running through Manuel Pellegrini's pre-match quotes, it is that the modern-day, free-scoring City bend for nobody these days. They were, he said, the "biggest team" in Manchester now and the most important thing was to carry on playing as they have all season, keeping the ball, pressing the opposition and backing their own ability to beat anyone. Messi was mentioned almost as an afterthought. "He's the top player in the world," Pellegrini said. "He's very important but I don't think Barcelona is just Messi."

His team were "not going to think just about defending; what we do with the ball is the most important thing. It's very important when we get the ball Barcelona chase us. They can get tired chasing us."

Pellegrini, in other words, wants to beat Barcelona at their own game and, if nothing else, you have to admire his boldness. Yet it does leave a question about whether City might be playing into Barcelona's hands, if it also means Messi has the space to be at his most devastating. "It's a problem," Yaya Touré said. "For me he is the best. OK, Cristiano Ronaldo won the last Ballon d'Or but Ronaldo's unlucky to find himself in the Messi era, and this era is about Messi. If Messi hadn't had that injury, which kept him sidelined for a month, I think he would have won it again."

Another manager might ask Touré to help nullify that threat by curtailing those surging runs from his starting position as a defensive midfielder. José Mourinho sometimes used Pepe in this role at Real Madrid, specifically to patrol Messi's favourite part of the pitch. But Pellegrini shook his head. "Yaya plays the way I want him to play," he said matter-of-factly. "I want him to be free."

It is a calculated gamble. Dietmar Hamann made the point recently that Touré, for all his obvious qualities, was guilty sometimes of leaving too much space behind him. Touré, he said, could be a "liability".

"We have a lot of respect for our old players but sometimes they are wrong," Touré countered. "For me, they are not important people. The most important thing is what my manager tells me to do. I'm in the right place. Liability or no liability, I've been playing for a long time. I have been playing in this position for a couple of clubs and I have a lot of experience."

Touré, preparing to come up against his former club, also used the word "stupid" to describe Hamann's analysis, but the German does know a thing or two about that position. Bayern Munich and Chelsea have both exploited Touré's licence to roam this season and the tactic, as he puts it, of "going where the ball goes". The trick is getting the balance right, otherwise the fit-again Fernandinho could be badly exposed as the last line of cover. For all his talk about the importance of "continuing our style of play, our personality", Pellegrini still used James Milner to double-up with Pablo Zabaleta on Eden Hazard as City eliminated Chelsea from the FA Cup on Saturday. One idea under consideration is for Javi García to play alongside Fernandinho and Touré to move further forward.

Chelsea's tactic against Barcelona has often revolved around ceding the wide areas, concluding that there is not a great deal of danger to come from crosses, and congesting the centre of the pitch, funnelling Messi's runs by using a strategically narrow team shape. Even then they are quite happy to admit they also needed an extraordinary amount of good fortune, including Messi thudding a penalty against the crossbar, to survive the onslaught of that epic 2012 semi-final.

Ferguson, like Pellegrini, wanted to be adventurous but now thinks he should have thought more about trying to stifle Barcelona's tormentor-in-chief. "After the inquest I told myself: 'When we play Barcelona next time in a Champions League final, I would have [Phil] Jones and [Chris]Smalling, or Smalling and [Jonny] Evans, right on top of Messi.' I wasn't going to let him torture us again."

Yet Pellegrini made the point that Barcelona are a "different team now", meaning not quite as formidable, and that it was always going to be "very difficult for them to continue at the same level as three years ago". Barcelona are still holding off Real Madrid and Atlético Madrid at the top of La Liga, by virtue of a plus-52 goal difference. They also have a four-time Ballon d'Or winner who, at 26, has just set a record for the highest number of goals, 337, by one player at a Spanish club. "I have never seen Messi play badly," Pellegrini said. "He's either excellent or great. We hope to face the worse Messi – the great one."