In Portugal they speak of Hugo Viana working “in the shadows”, a man eager to perform his duties away from the spotlight. He will be especially pleased that his good friend Rúben Amorim will take the headlines when Viana’s current and future employers meet in the Champions League on Tuesday night. Over the past six years he has built his reputation as one of Europe’s best young sporting directors by helping to make his first club, Sporting, a force once more.

Sporting had not won the league title for 16 seasons when Viana arrived with only six months’ experience at Belenenses. Under Viana’s direction, Sporting have bested both Porto and Benfica twice to finish top – his first title coming in his third season at the club. The former Newcastle midfielder cannot claim all the credit for the turnaround but it was his decision to appoint his former teammate Amorim, paying €10m for a head coach who had started the season managing Braga B in the third tier.

The duo’s success means they will become rivals in Manchester; Viana will soon be tasked with keeping the City train running and Amorim with trying to turn the United ship around after years of drifting. Working collaboratively is one of the key factors in the two men growing their reputations and whether they can slot into two very different environments and maintain their progression will be fascinating to watch and may even test their bond.

“I think one of the best things that Viana did was to bring the people that he trusts like Amorim,” Viana’s former teammate Hélder Barbosa says. “He’s a young coach and the people start talking a lot about the money they spend but right now everybody talks that he was not a cheap coach but probably he’s the best coach in Portugal right now and he’s young, so they are closer than ever before.”

Viana, however, has not built a career on the back of friendships. He is willing to be ruthless and take risks. He quit Belenenses after falling out with the president and sacked coaches with great regularity in his early days at Sporting in the hope of finding the right formula.

When City were searching for a replacement for the departing Txiki Begiristain, the research was extensive. There was no chance the club would settle for someone they saw as second best. Quique Cárcel was another prime candidate for the position as director of football but he was left in post at one of City Football Group’s other clubs, Girona.

Barbosa commuted to Braga training with Viana and says: “I never expected that he would continue in football after retiring because we never talk about the players or scouting in the car. We always spoke about football in general but also about business because he had a lot of businesses before. He gave me a lot of advice before on how to spend my money, how to think about the things, because this guy thinks in front of everyone.”

Benfica and Porto were often able to mine talent, especially in South America, bringing in relatively cheap players with potential who required nurturing, alongside academy products. Viana knew he would have to expand the scouting network at Sporting to get them back on a level footing with their bitterest rivals. Over the past summer, Sporting’s four signings arrived from Denmark, Belgium, Mexico and Poland, helping them sit atop the league after 10 consecutive wins. He is regarded as good to deal with, a clear communicator and honest in his assessments in the market, and is helped by a strong relationship with the agent Jorge Mendes.

“Because he was a player, he knows how to speak with the players, the way they think, and it’s better for all of the players if you have someone that played before and he knows what you need,” Barbosa, who won his solitary Portugal cap alongside Viana, says. “He is one step in front of everyone. He was a very good teammate and as a director he has the same good advice and has not changed.”

From Coventry to Toluca, Viana has helped supply Sporting with a conveyor belt of talent to counteract the selling of those who have outgrown Portuguese football. Manuel Ugarte, Pedro Porro and João Palhinha have come and gone under Viana’s watch. All were regarded as investments, none were cheap but there was belief they could grow at Sporting and be sold on to ensure the club is profitable.

“He’s a very quiet guy but I never saw Viana being very nervous about things,” says Barbosa. “Even if he’s nervous, he can be very calm talking.”

Regardless of how good the players are, getting them to perform is not guaranteed and finding and backing the right head coach is imperative. Viana’s bond with Amorim has helped put Sporting back on the map. Amorim is regarded as the most overperforming coach in Europe, working wonders with the comparably limited means.

“Before Viana gets to Sporting, everybody talks about Sporting for bad reasons,” Barbosa says. “All the fans were unhappy, the organisation was not good. Everybody knows what’s happening inside of the dressing room and these kinds of things. In six years, everything changed and Sporting is better than ever.”

There is a cloak around Viana, a man so far away from the limelight it is difficult to shine much on him. He has a very close circle of trust but he will need to adapt to a change of scenery, where his closest ally is set to become an enemy.