Du Plessis explained how De Villiers' absence had an affect on him as then South Africa captain.
De Villiers put a sudden full stop to his illustrious career at the highest level in 2018, citing excessive fatigue from playing all three formats and lack of time with his wife and growing kid as major reasons.
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For South Africa, that left the side substantially understrength a year before the 2019 World Cup and meant a lot of headache for Du Plessis in terms of rebuilding of the side after the loss of their best player.
"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," Du Plessis told India off-spinner Ravichandran Ashwin on the latter's YouTube channel for 'DRS with Ash'.
"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."
"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," he added.
After enduring a disappointing campaign in UK, either side of which the Proteas were whitewashed 3-0 in Tests in India and lost home series to Sri Lanka, England, Du Plessis resigned as captain last winter, with those lacklustre results coinciding a poor run as a batsman for him.
"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," said the 36-year-old right-hander.
"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.
(Inputs from ANI)