The 22-year-old placed second in Saturday’s 16.8-kilometre test, 18 seconds behind Jon Izaguirre (Movistar) but one second ahead of Fabian Cancellara (Trek-Segafredo) to move into the overall lead.
With one further examination to come – Sunday’s 117-kilometre final leg takes in the Albula and Flüela passes before the finish in Davos – Lopez lies just 8 seconds clear of Andrew Talansky (Cannondale), while Izaguirre (3rd at 16 seconds) and Warren Barguil (4th at 18 seconds) remain very much in contention.
Speaking after taking possession of the yellow jersey on Saturday evening, Lopez was under no illusions as to the task ahead of him on the concluding stage. “Tomorrow it will be a war, but I'm ready,” Lopez said.
Winner of the Tour de l’Avenir in 2014, Lopez turned professional with Astana last season and delivered a string of strong performances, including 7th place overall in his debut Tour de Suisse. In the absence of Vincenzo Nibali and Fabio Aru, Astana handed the reins of leadership to Lopez for the Swiss race once again this year, and he has been a model of consistency this week.
After finishing with the group of favourites on the mountain stages to Carì and Amden, Lopez showed his hand by placing second to Tejay van Garderen (BMC) on the Rettenbachferner, a display that moved him up to second place overall. The Davos time trial has pushed him to the cusp of a bigger prize.
“I’ve had good sensations and I have the physical condition to get a good result,” Lopez said. “We came here with the aim of doing a good race, knowing that I had been 7th overall here a year ago. The aim this year was to improve on that finish, to get a good placing on GC. There’s a day left now and we’ll fight to the end.”
Astana directeur sportif Dmitriy Sedoun – who was manager of the defunct Astana Continental team during its spate of positive tests in 2014 – explained that Lopez had prepared for the Tour de Suisse as though it were a Grand Tour, by reconnoitring the key stages ahead of the race.
“I'm not really surprised. I expected he could do well. Along with Miguel Angel we started thinking about this race already this winter and before the start of the Tour we tried all the stages,” Sedoun said in a statement on the team website.
"He's only 22 years old and he started to ride a bike five years ago and therefore still has much to learn. Having the leader's jersey is the signal that he is doing a good job."
On Friday, Lopez was named alongside Nairo Quintana (Movistar), Rigoberto Uran (Cannondale), Sergio Henao (Sky) and Esteban Chaves (Orica-GreenEdge) in Colombia’s team for the road race at the Rio 2016 Olympic Games.
Lopez is not, however, in contention for Astana’s Tour de France team. Instead, the youngster is expected to make his Grand Tour debut at the Vuelta a España in August.