Chris Froome says "nothing is impossible" after his historic Tour de France and La Vuelta double.
The 32-year-old Briton on Sunday completed victory in La Vuelta to become the third rider to win the Tours of France and Spain in the same year and the first since the Vuelta was moved to its current position in the calendar in 1995.
Froome has long eyed May's Giro d'Italia from afar, knowing the Tour is his priority and it will likely remain so in 2018 when he will seek a fifth yellow jersey.
His achievement in the last three months has led some to suggest he could target all three grand tours in the same year.
Stephen Roche, who in 1987 won the Giro, Tour and the Road World Championships title, reckons it would be "humanly impossible".
Asked if winning the Giro, Tour and Vuelta was a realistic aim, Froome told BBC Radio Four's Today programme: "I wouldn't say it's impossible, nothing's impossible, but certainly it would take some doing."
Froome has won four of the last five Tours and had finished runner-up in La Vuelta three times [2011, 2014 and 2016] before claiming the red jersey this year.
Belgium's Eddy Merckx won a record 11 grand tours in his storied career and was known as 'The Cannibal' due to his appetite for victory.
Asked if he could hope to target Merckx's achievement of 11 wins, Froome said: "A completely different era. Eddy Merckx's time of racing, he was able to win every single race on the calendar. The sport is transformed since his time."
One of the recent transformations has been the dominance of Team Sky.
Team Sky have won five of the last six editions of the Tour de France, with Sir Bradley Wiggins triumphant in 2012 before Froome's wins in 2013, 2015, 2016 and 2017.
"We're not going to change what we're doing. It's obviously a winning formula," Froome added. "The team is super strong and we're extremely proud to have the backing of a sponsor like Sky, who are behind us all the way."