De Villiers had retired from international cricket in May 2018 and Du Plessis said that after this decision from his friend, he started wondering as to how "the team will move forward".
"When AB left, it was really tough for me, because I depended a lot on him, as a friend, and obviously as the best player in the team, we needed his skills. When he told me that he was done with international cricket, as a friend, my first instinct was -- I'm here for you, and I'll support you, if you feel like you're at the end of your career and you don't want to do it anymore, then that's okay - I support that decision 100 per cent, " du Plessis told Ravichandran Ashwin on the latter's official YouTube channel.
"As a captain, I was like how do we move forward without AB, how do we get the same performances But the friend in me trumped the captain in me. And I just said, we're going to miss you, are you sure? He was like, yeah, I am 100 per cent sure, I don't want to play international cricket anymore. I don't have the drive to do it anymore. So I am stopping. I respected that immediately and left it there. I never ever after that tried to convince him again, because I respected what he said. Even at times when we desperately needed him," said du Plessis.
Under the leadership of du Plessis, South Africa failed to reach the semi-finals of the 2019 World Cup, and sometime later, du Plessis stepped down as the skipper of the side.
"The last year of international cricket for me was tough, because I carried a lot of what was going through the team's performances on my own shoulders, and I didn't want to show that to anyone, because in my own head, I am the captain, I had to make sure I stay strong for the team," du Plessis said.
"That for me was the hardest thing to do myself, purely because I've believed that being a leader is something that was part of my purpose. And I've always enjoyed captaining more than I have enjoyed playing. I think I am a good player, but I think I really come to the party when it comes to captaining. That's when I really love playing cricket. That's what puts a smile on my face," he added.
South Africa was clean swept at home by Sri Lanka in a two-Test series, then the side lost 3-0 away in India, and was beaten 3-1 by England at home.
Du Plessis would now be in action for Chennai Super Kings in the upcoming Indian Premier League (IPL) 2020.
CSK would face Mumbai Indians in the tournament opener on September 19 in Abu Dhabi. (ANI)