Madrid landed Courtois from Chelsea in the summer transfer window, and he was expected to be an immediate starter. However, Lopetegui has stuck with Navas for the first two games of the La Liga season, with Los Blancos winning both.
When asked about the choice after the 4-1 win over Girona on Sunday, Lopetegui said he will be taking the decision on a game-by-game basis, per Sacha Pisani of Goal:
"It's not a situation that's easy to understand, but it's simple enough to explain. I've got some really good options in goal and there are no problems in that area. We'll decide what's best for each game.
"Keylor got the nod today and did very well. There's great competition and that makes us stronger in the goalkeeping department. I've got some thoughts in my mind, but I'm not going to share them. Over the course of the season, I'll look for solutions to solve the next immediate challenge."
Lopetegui's faith in Navas means that Courtois has yet to make his debut for Los Blancos following his move from Chelsea.
As The Spanish Football Podcast noted, there's an increasing focus on the competition for places in goal at the Santiago Bernabeu:
While Navas has been a key part in Madrid winning three
The Costa Rican has always been capable of producing excellent saves and is as good a shot stopper as any in La Liga. However, his game can often be punctuated by errors—he made high-profile ones against Juventus and Bayern Munich in the Champions League last term.
However, it appears the extra competition for places has brought the best out of Navas early in 2018-19, as he's been excellent in the two matches so far.
As Spanish football journalist Rik Sharma noted, Navas played a crucial role in the buildup to Gareth Bale's goal on Sunday:
Courtois will be desperate to make his maiden bow for the European champions, although the patient approach taken by Lopetegui in regards to his integration does make sense.
Not only was the goalkeeper involved in a high-profile transfer saga, he was also part of the Belgium team that made it to the semi-finals of the FIFA World Cup, eventually finishing in third place. Over the course of the campaign, this extra time off may keep Courtois sharper for longer and especially in the business end of the term.
Eventually, the former Chelsea man should take his place as first choice, as he's got more positives to his game than his rival for a starting spot. The fact that Navas is unwilling to give up his jersey without a fight and has raised his game gives Lopetegui a good problem to have.