Growing up in Federer's shadow, Wawrinka used to ask for advice, from how to beat certain players to how to deal with pressure.
"Then the day came where he didn't call me so much any more," Federer said in Melbourne, where on Thursday he and Wawrinka will meet in the semifinals of the Australian Open.
"He called me less and less. I also felt like I didn't tell him anymore, because he created his knowledge, his base, had his team. Only from time to time would I give him advice if he asked me."
Sometimes Wawrinka would return the favor, but mostly it came from the former world No.1.
"It has happened," Federer said. "But it has been 95 percent of me giving him advice."
The two Swiss have been friends for years, sharing many great moments, including an Olympic gold medal in 2008 and a Davis Cup triumph in 2014.
As he racked up his 17 Grand Slam titles, Federer was top dog, but three majors in the past three years has given the 31-year-old Wawrinka belief that he is on more of an even footing.
"For sure now I'm more confident with myself," said Wawrinka, who won the US Open last September. "When I step on the court, doesn't matter who I play, I know what I have to do if I want to win.
"For sure, against Roger, it's always special because he's so good. He's the best player of all time. He has [an] answer for everything. But I managed to beat him in a Grand Slam [at the French Open], so we'll see. Most important is that I step on the court and I play my best tennis."
Wawrinka's emergence from Federer's shadow really began in May 2013, when Wawrinka began working with coach Magnus Norman, the Swede who reached world No. 2 as a player and made the French Open final in 2000.
Norman gave Wawrinka the belief in his ability he needed, and he won his first Slam title at the Australian Open in 2014, before going on to beat Federer to win his first Masters 1000 crown in Monte Carlo in 2014, his favorite match against Federer.
After a six-month injury layoff, few expected Federer to get this far in Melbourne, but with an 18-3 record against Wawrinka, he says he believes he can get to another Grand Slam final at the age of 35.
And when they walk out on Rod Laver Arena on Thursday evening, Norman admits Federer might still have a psychological edge.
"If you look at the way he was playing against [Kei Nishikori in the fourth round] and also the matches before, I think everybody knows that Roger is the favorite," he said after Wawrinka's win over Jo-Wilfried Tsonga in the quarterfinal.
"Roger is Roger; it doesn't matter if he's ranked 17 or when he's playing like he was a few nights before against Nishikori, you feel like his level is there for sure, his confidence is there, his movement is there and he's as good as he has always been."
Federer thrashed Wawrinka the last time they played in a Grand Slam, at the US Open in 2015, when conditions were just as fast as they have been here this fortnight.
But what has also changed is that Wawrinka generally improves as tournaments progress, and he has won all three of his major finals.
"That's also there somewhere," said Norman, who feels Wawrinka has not quite hit top form yet here. "That's for sure an advantage for Stan."
And even if Federer comes flying out of the blocks, as he tends to do, the chances are that Wawrinka won't panic.
"That's one of the things he really improved," Norman said. "He's more calm. He knows that the longer the match goes the better his chances are, so he's more calm in the beginning of matches. That's one of the things that he improved a lot."