In six days, Bradley Wiggins begins a challenge that could turn out to be even greater than that of last year, when the "Kid from Kilburn" won the Tour de France and added Olympic gold 10 days later. The Giro d'Italia, which starts on Saturday in Naples, is cycling's biggest stage race after the Tour; Wiggins is making his first attempt at winning it, and – depending on the form of Sky's designated Tour leader Chris Froome – he may then go on to attempt the legendary "double" of Giro followed by Tour de France.

The turnaround in Wiggins' fortunes since 2010, when he joined Team Sky and had a disappointing year – albeit one in which he won the prologue time trial of the Giro and wore the legendary maglia rosa – has been masterminded by Tim Kerrison. The former rowing coach and sport scientist with the Australian and British swimming teams was brought to Sky from British Swimming when the team was formed. In 2010, recalled Wiggins, "Tim started asking all kinds of questions ... stuff an outsider to cycling might ask. He wrote down all the demands of the Tour and we went from there."

In characteristic style, Kerrison breaks down the big challenge into two parts. "We aren't looking much past the Giro at the moment. The biggest challenge with the Giro is that we know what it took to get it right for the Tour – we had six or seven months from November but you have to do it in two months less for the Giro. I feel we've ticked all the boxes. The difference this year is that Brad is trying to focus on skills he needed to develop for the Giro – limiting his time loss on climbs, being responsive to the punchier climbers on climbs, being in contention without a long flat time trial." That change of focus explains why Wiggins will go into the Giro without a solo win, whereas he hit the Tour last year with three major stage race titles under his belt.

As for Wiggins riding the Giro and Tour with his eyes on high overall placings in both events, Kerrison says he is "not interested in anyone saying something can't be done. There are a lot of myths and assumptions. A Grand Tour is very demanding but a month is a long time to recover. The transition from Giro to Tour is very achievable. [Brad] can recon the stages, recover, and focus on doing his job in the Tour, whatever it is."

If Dave Brailsford is the high-profile front of Team Sky, Kerrison is the quiet man in the background, the one who tends not to get noticed although Wiggins has referred to him as "the guru". He started out competing as a rower in the late 1980s – "not a particularly good one" – then moved into coaching, "because I realised I didn't have the talent to be the best as an athlete," working at the Queensland Academy of Sport (QAS). His biggest success story as a rowing coach was Marguerite Houston, who won a world title in record time at lightweight women's quad scull in 2002.

Initially, Kerrison was holding down full-time jobs coaching, rowing and swimming, but in the run-up to the Athens Olympics he moved to swimming, still with the Queensland Academy of Sport. There is a misconception, he says, that he worked with Ian Thorpe, but that is not the case. At the QAS, he and a fellow coach, Shannon Rollason, decided to work on the women's sprint, a weak area for the squad, which had a strong record in distance swimming.

"We began a little project changing the way the women's freestyle sprinters trained, stripping it back to first principles, and came up with the concept of reverse periodisation." This inverts the traditional precept that intense work is brought into training on top of an endurance base; instead, intensity is included from the start and is seen as part of the foundation. Their two-year project culminated at the Athens Olympics in 2004, where Jodie Henry won three gold medals in three world record times, in the 100m freestyle, the 4x100m freestyle relay, and the medley relay, becoming Australian Swimmer of the Year.

His core principle, across all three sports, is that of tabula rasa – you move away from the past and begin again from new. "I've always resisted looking at how people have done things in the past. I prefer going in and looking at a sport, the demands of the event, the competition, the psychology, the physiology, biomechanics, and then what is the best way to develop a human being to achieve that. When you look at the past, it biases things going forward. Over time you pick up snippets from the past, but I've never liked looking back. That's why some of the things I've come up with are so fundamentally different."

Kerrison believes that swimming coaches are obliged to think outside the box. "They are by far the most creative of all coaches, because it is a pretty boring sport. In swimming you can die of boredom; in cycling the terrain creates variety and there is a social element as you ride. In swimming you are stimulated by variety within the coaching." He came to cycling knowing nothing about the sport, but says: "That naivety was a strength. I could ask a lot of stupid questions; luckily people were patient and generous."

The lack of structure in professional cycling coaching meant that, when properly coached, Sky's riders had a considerable margin for improvement. "It was quite amazing how much scope there was to work with these guys. The British and Australian guys were much more coachable because they'd come through a system, but it can take a long time for someone who has never been coached, who isn't used to structured training efforts, to work with a coach, to get their heads round the level of prescription they are given." If Wiggins has responded best of all, that's not surprising: "He's so coachable, because he's already been coached all through his life; other guys are learning to be coached for the first time."

Kerrison believes professional cycling teams have had a tendency to spend their money on buying riders rather than on getting the best out of them, and again that has created a gap for Sky to exploit as they have developed a coaching network that has expanded from one coach in year one, to four this season. "Other teams have spent on recruiting riders but it doesn't make sense buying in the best then hoping. You can see from this team how much you can get by investing relatively small amounts in coaching. The gains are disproportionate. It's so obvious that it's a shock other teams aren't doing it."

The bare bones of Kerrison's approach is that he has looked at every area of the Giro, broken it down, and then created graphs in which one line shows the riders' performance in a given area, another the required performance. Training is tailored to make the lines converge. Wiggins credits Kerrison, variously, with getting him to him race less, making him use races as practice for leading the Tour de France, working on his core strength – an area he had ignored – working on his fitness for climbing steep hills and making him time trial at lower pedal revs and larger gears.

Kerrison, however, is keen to refute the notion that Sky are "all about numbers". Critics have said the team simply ride to the power outputs on the computers on their handlebars in a rather soulless way, but he says: "We use numbers for training but race on feel. We use the numbers for feedback, but if you are over-reliant on it you would be lost when the numbers aren't there. All this about us racing to numbers isn't what happens. We train the guys to race without SRMs [the computers that cyclists use to measure power] – sometimes they cover them up because it's important that they can ride on feel."

As well as the accusation of robotic training and racing, Sky have been hit by the fact that in the post-Lance Armstrong era, success for riders and coaches comes at a price: suspicion that it is being achieved through illicit means. "People will question me," Kerrison acknowledges. "The better the job you do, the more people question it. If it's done fairly, they have the right to have suspicions because there have been plenty of riders and teams who have insisted they were clean and have turned out to be far from the case. Initially, for anyone faced with that, the reaction is very similar – it's anger, you don't know how to respond to it. I went through that adjustment last year, Brad's been through it, Froomie has and Richie Porte [Sky's Australian rider who this year won the Paris-Nice race] will go through it. Last year with everything we learned about the US Anti-Doping Agency, Tyler Hamilton, Lance Armstrong, that helped us understand that the public are at a point where they don't know who they can trust. We have to earn everyone's trust again."