He jokingly compared it with making the first call to his close friend and Mercedes team principal Toto Wolff after tempting his driver away.
Vasseur expects that despite his obvious disappointment in losing his seat, Sainz will remain fully dedicated to the Ferrari cause this year, insisting that the team will continue to support him.
“As you can imagine it was not the easiest call of my life, one of the most difficult, with the one with Toto!,” said Vasseur when asked about giving Sainz the bad news.
“But I'm fully convinced that he a very professional driver, that he understands that it's a long season in front of us, that it's a huge opportunity.
“And I think it's also a dream to be in this situation, to have the team behind him. We had a long discussion, so as you can imagine I will be fully supportive of Carlos. He is fully committed, and we know that we have to do the job together. Together we are professionals."
Expanding on the Spaniard’s commitment he said: “I'm fully convinced that Carlos will be fully dedicated and fully committed to the season until the last lap and the last corner of the season, and equally I'm sure that all the team will be fully motivated and fully behind Carlos, who did a great job for us so far.
“Now it's important for us again to be focused on 2024. We have a good opportunity, we work so hard on the project that I don't want to have any kind of distraction.”
Vasseur was reluctant to say much about Hamilton given that Tuesday’s media activities were about the launch of the 2024 car rather than the longer term, but he did some indication of what his arrival will mean for Ferrari.
“On the announcement that we made last week regarding Lewis, it's a huge opportunity for the team for sure,” he said. “We are sure that he will bring us a decent step for the future, I think it will be a good challenge for everybody.
“But we want to be focused on 2024. We don't want to have any kind of distraction. And it's also why we made the announcement so early because it was important for us to all over the season to be focused on 2024.”
Asked if he thought having to make way for Hamilton was unfair on Sainz he said: "Unfair? I don't know if it's the right word. Because I think for the team the opportunity of Lewis is something that you have to consider in any case, he is the guy with the biggest experience, and so it’s a huge opportunity for us.
“It has nothing to do with Carlos. Carlos did a great job last year, I'm sure that he will do a great job this year. He's very professional. We have a very good personal relationship. But it is like it is, and we have to be focused on the future."
