BAYONNE, France (VN) — The Giro-Tour double remains safe for now.

Chris Froome (Sky) and Tom Dumoulin (Sunweb) came as close to knocking off the Giro d’Italia and Tour de France double as anyone in the past two decades. Froome won the Giro and will stand third on the Tour podium Sunday. Dumoulin was second in both.

Why did they come so close this season to pulling off the first double of the modern era? The key to a modern attempt at winning the Giro d’Italia and Tour de France back to back is an extra week of recovery.

“The extra week in between made a difference,” Dumoulin said. “That was the main reason I decided to do the Tour.”

This summer’s World Cup prompted Tour organizers to move its race back an extra week on the racing calendar so its marquee event would not overlap too much with the wildly popular soccer tournament held every four years. The Giro ended May 27 and the Tour started July 7.

That month-plus window had ripple effects that played out across this season. The resulting extra week of down time between the Giro and Tour was instrumental in Froome and Dumoulin deciding to go for the double this year.

Perhaps it’s not coincidental that the last rider to achieve the double — Marco Pantani in 1998 — was also during a World Cup calendar year.

Can an extra week in between the two races really make such a big difference?

Those extra days counted a lot for Dumoulin, who said he wasn’t seriously considering racing the Tour until his body recovered from the hard effort at the Giro. Froome said the extra week this year between the Giro and Tour was decisive in his commitment to racing and eventually win the Italian grand tour.

“The extra week because of the World Cup was a decisive factor and part of my decision in trying to do the double,” Froome said. “Tom finished second in both grand tours, so it shows you can do both races at an extremely high level, which leads me to believe we can win both of them in the same year.”

Of cycling’s milestones, the modern Giro-Tour double has proven among the most elusive. It’s possible to win two grand tours in one season. Retired Spanish star Alberto Contador won the Giro and Vuelta a España in the same season in 2008. Last year, Froome became the first rider to win the Tour and Vuelta back-to-back since the Spanish grand tour moved to late summer.

Pantani’s achievement of being the last pro to pull off the Giro-Tour double stands even though Dumoulin and Froome came as close as anyone has since Contador won the Giro a second time in 2015 and hung on to finish fifth in the Tour nearly 10 minutes behind Froome.

Despite falling short this summer, Froome seems convinced the double is attainable. The Sky captain won three consecutive grand tours and tailored his training to hold a longer higher level than one focused peak. He won the 2017 Tour in less convincing fashion, but he also had more gas in the tank to target the Vuelta and the double this season.

“I still believe it’s possible to do the double,” Froome said. “I won the last three grand tours, so I still believe it’s possible. It’s not going to be this year, that’s for sure.”

Riders say the Giro-Tour is the most challenging to tame for a variety of reasons. The Italian grand tour’s demanding course leaves winners with “Giro fatigue” going into the Tour, the hardest and most severe of the season. The Giro’s unpredictable weather is another factor as rain, cold and even blizzards can strike the Italian mountains at any time. Racers also say the Giro is as hard as the Tour and the day of riding “piano” are long gone.

Grand tour riders insist it’s easier to manage fitness by targeting the Tour first and then hanging on through the Vuelta. Froome was second three times in the Spanish grand tour before finally winning it last year. For Froome, the Tour was always the top goal. The Giro, however, requires an earlier peak, often leaving the Giro protagonists racing on fumes in the final decisive week of the Tour.

“I could take it super easy for two weeks without stressing about my shape,” Dumoulin said. “I knew there would be enough time to build up again.”

Another factor is the Giro’s recent excursions to far-away starting points that require the race to start a day earlier — on a Friday instead of a Saturday. That means riders need to travel earlier and longer to get to the Giro, such as this year’s Giro start in Israel. One day might not seem like a lot, but when it comes to travel, recovery and preparation, a day or two counts when trying to win back-to-back grand tours.

“Next year it’s going be a week less so there will be only three and a half weeks,” Dumoulin said. “I think next year whoever wants to go for the challenge to do the Giro and Tour, that would be pretty impossible in my eyes.”

Recent double efforts reflect the importance of an extra full week between the Giro and Tour. Last year, Nairo Quintana (Movistar) finished second to Dumoulin and struggled to a career-worst 12th in the Tour. Contador won the 2011 Giro and lacked winning spark in the Tour as he fought his clenbuterol case in the background.

So why not simply stretch the calendar out and permanently make it five weeks between the Giro and Tour instead of just when the World Cup comes around every four years? There are a few factors to consider.

If the Giro was pushed earlier on the calendar, there would be a higher chance of worse spring weather in the Dolomites and Alps. An earlier Giro would also butt up against the spring classics, making it difficult for the classics riders to race the Giro.

Pushing the Tour later in the calendar creates headaches for organizers trying to book thousands of hotel rooms in late July or even early August that is the peak tourist season in France. Traffic issues and road closures also become more complicated later in the summer across France.

If the Tour was shifted later, that would also mean the Vuelta would have to start in early September. And behind that, the world championships would be nudged into early October. Right now, the Vuelta likes its earlier dates so it can draw on late-summer holiday crowds in Spain and the UCI prefers its late-September worlds window for the hope that the weather holds in Europe.

As it stands now, all the leading interests prefer the international calendar just as it is.

Without the World Cup, the calendar reverts to its four-week gap between the Giro and Tour in 2019. The Giro will end June 2 and the Tour will start July 6.

“If you want to do the Giro-Tour double, then three and a half weeks isn’t enough time,” Dumoulin said. “That is my opinion and I think a lot of riders think the same.”

This could mean that Pantani’s mark as the last rider to pull off the Giro-Tour might stand for a while — or at least until the next World Cup in 2022.