The pair celebrated victory at UEFA Euro 2016 together, with Sanches joining Bayern immediately after being named the Young Player of the Tournament. He was unable to hit the ground running in Bavaria, however, and a spell out on loan at Swansea City ensued before he returned to Munich in the summer.
Watch: Sanches delighted to be back in action with Bayern
Heralded by Joshua Kimmich as Bayern's match-winner in their Matchday 9 win over Mainz, Sanches is now starting to deliver on his earlier promise and Nani says he is not surprised, as he expects even bigger and better things to follow from his compatriot.
"It's only normal that young players are not immediately ready to play regularly and know everything," he told Bild newspaper. "But now I think that, with his maturity and experience of playing at another club, he's going to explode and be able to show off all of his talent.
"He's a good lad and he's going to be extremely valuable to Portugal and Bayern."
The 21-year-old already proved that in the summer of 2016, and Nani is certain that fans witnessed the real Renato Sanches back then, and not the one who had initially struggled to find his feet in the Bundesliga.
"He started playing really well, really early," added Nani, who now plays for Sporting Lisbon after spells with Fenerbahce, Valencia and Lazio. "He had a dream start, winning the European Championship as the best young player.
"His energy was extremely important for us. I know that not many players have achieved what we did [in 2016]."
Sanches has played a role in Bayern's past six Bundesliga fixtures, while he scored his first goal for Bayern against his former club Benfica in the UEFA Champions League in September, earning plenty of plaudits. And with Thiago Alcantara sidelined for a month, he can expect even more starts over the coming weeks, and the chance to prove himself.
"I'm feeling really good and above all prepared," Sanches said following Bayern's midweek DFB Cup win over SV Rödinghausen. "Of course I'd like to play more often, but there are so many internationals in our squad. When I get the chance, I will definitely do my best to help the team.
"Sometimes you just need patience and to give yourself some time to get used to certain things and to settle in. Now I feel ready."
Ready, as Nani says, to explode.