Tragically, Carter was in a fatal auto crash while on his honeymoon in South Africa - just one year before Federer won his first title in 2003.
But as Federer himself put it, he has rarely if ever "broke down" in an interview the way he did when talking to CNN's Christina Macfarlane from his training base in Dubai last month.
Federer will be competing in the Australian Open this year as the world no. 3 and the defending champion in a bid to win his 21st Grand Slam title and a record 7th Australian Open title as well. "I was able to, you know, have coaching lessons with him".
"I guess it was somewhat of a wake-up call for me when he passed away, and I really started to train hard". "Peter was really a really important person in my life because I think if I can say thank you for my technique today, it's to Peter".
"I never thought I was going to hold a trophy", he told CNN.
"I think what I would like to say is that I've been incredibly fortunate to having had the right people at the right time".
The Australian newspaper reported he left his hotel and "ran through the streets, bawling and hysterical". "He didn't want me to be a wasted talent".
Even though Federer has spent only two weeks at home since August, the 37-year-old said being on tour now in the "back end", of his career was his most enjoyable period.
Murray's hip surgery meant he played just six events in 2018, and Nadal's truncated 2018 campaign was bookended by injuries that forced to him to retire in both the Australian and US Opens.
Forget champagne and victory parties, Novak Djokovic has a different celebration in mind should he win his seventh Australian Open title: climb a tree.
Recounting how they first met at the Old Boys' Tennis Club, Federer said: "He was one of the star players on the team. I made those decisions, but I've been lucky along the way".
"In terms of who is going to win it, we know who the usual suspects are and I am part of that bunch".
The world number two also endured a disappointing Australian Open exit past year, forced to retire in pain from his quarter-final with Marin Cilic. Worryingly, he pulled out of the Brisbane International last week with a thigh strain but then played an exhibition in Sydney and insists he will be ready for Melbourne.
"I have a friend there, a Brazilian fig tree, that I like to climb and I like to connect with so that's probably my favourite thing to do".
"They used to call each other and say "I have this really special kid I'm training" and Darren would say the same [about Hewitt] from Adelaide".