The Costa Rican joined PSG in September from Real Madrid as Alphonse Areola moved in the other direction, and on Wednesday his late penalty save helped secure a 1-0 win over Club Brugge that clinched his side's place in the last 16.
The last line of defence for Real as they won three successive Champions Leagues between 2016 and 2018, Navas is yet to concede a goal in Europe since arriving in Paris.
Indeed, the 32-year-old has let in only five goals in 12 matches for Thomas Tuchel's side.
"He is an extraordinary goalkeeper. He won three Champions Leagues with Real Madrid in a competition where goalkeeper is such an important position. They can change the outcome of a game," remarked midfielder Marco Verratti after Wednesday's game, in which Mauro Icardi scored the winner.
"He will bring so much experience and calmness to the side," said sporting director Leonardo.
Leading sports daily L'Equipe on Thursday gave over its front page to the goalkeeper with a headline referencing 1982 Jean-Paul Belmondo action comedy The Ace of Aces.
And yet less than a week ago it is true that Navas hardly covered himself in glory as PSG suffered a shock 2-1 defeat at Dijon.
Then again, neither did any of his teammates, and Europe is where this team will really be judged. A trip to Real Madrid later this month, when Neymar should be fit again, could be revealing.
In Ligue 1, PSG have lost three of their opening 12 games and yet they are already seven points clear of Angers at the top.
They travel to face Brest on Saturday where Tuchel will again have to decide whether to leave the club's all-time top goal-scorer, Edinson Cavani, on the bench.
Icardi has been preferred to the Uruguayan recently and has now scored eight times in the last seven matches.
One to watch: Rudi Garcia
Few tears were shed among Marseille fans when Garcia left his job as coach at the Velodrome at the end of last season. In contrast, there was plenty of unrest in the Lyon support when the 55-year-old was appointed as successor to the sacked Sylvinho last month.
Garcia's recent past with Marseille was always going to be difficult to swallow for Lyon fans given the frankly bitter rivalry that has developed between the clubs.
On Sunday, Garcia heads back to Marseille with his new team for the 'Olympico' as the sides jostle for position in a packed table behind PSG.
Lyon are 10th but sit just four points behind Marseille in fourth and have won their last three games, including a precious 3-1 defeat of Benfica in the Champions League in midweek.
Garcia has been dealt a major blow, though, with the news that Memphis Depay -- scorer of 11 goals in 14 games this season -- will miss the match with a hamstring injury.
8 - The number of goals scored by Mauro Icardi in PSG's last seven matches.
5 - Lyon have won their last five Ligue 1 meetings with Marseille and are unbeaten in 10 encounters since a 4-2 defeat in May 2014.
10 - Lille are unbeaten in their last 10 home league games, a record they will hope to extend as they entertain Metz on the rebound from a 4-1 loss at Valencia which eliminated them from the Champions League.
Nice v Bordeaux (1945)
Brest v Paris Saint-Germain (1630), Lille v Metz, Monaco v Dijon, Reims v Angers, Strasbourg v Nimes (all 1900)
Rennes v Amiens (1400), Montpellier v Toulouse, Nantes v Saint-Etienne (both 1600), Marseille v Lyon (2000)