Four-time Tour de France winner Chris Froome penned a touching message on social media in memory of Team Ineos sport director Nicolas Portal, who died Tuesday of a heart attack.

The 40-year-old Frenchman, who joined the Team Sky staff in 2011 after riding with Froome in his final professional season with the new team in 2010, was responsible for Froome's four Tour wins and the Briton's 2017 and 2018 Vuelta a España and Giro d'Italia, and helped Geraint Thomas win the Tour in 2018 and Egan Bernal win the Tour last year when the team became Team Ineos.

In a message posted on Twitter and Instagram Thursday night, Froome called Portal "irreplaceable" and a "great friend," and included a photo of them together in Mont Ventoux in 2016.

"I have been speechless since hearing the news," Flume wrote.

"Aside from what a great friend, father, and husband Nico was, I don't think people realize how important and influential he was in the success of our team over the years.

"He is completely irreplaceable and I can't even imagine where he will go from here. He was with me through difficult times, picked me up whenever I doubted myself, and encouraged me to succeed in every way. He has left behind a truly phenomenal legacy.

"I will run in his memory and do everything I can to honor him and all he taught me," Frum wrote, signing his "love and thoughts" to Portal's wife and two children.