"I missed home. I'm very happy to start working to always give the best version of myself on the pitch," the Turkish midfielder said, before turning to his first sessions under the club's new head coach.
According to Turkish Football, Güler reported to Valdebebas ahead of schedule following Turkey's group-stage elimination, and coaching staff needed only a couple of sessions to notice his improved physical condition, with one member of the technical team said to have described him as "flying" in early drills.
That early impression appears to have made a mark, with Mourinho reportedly shaping a prominent role around the 21-year-old for the coming campaign.
Güler was full of praise for his new manager.
"It's a great opportunity for me to work with a legend like Mourinho. He and his team explain everything very clearly. They're also very honest off the pitch," he said.
On the demands of pre-season training itself, the midfielder added: "In this period, the most important thing is working on the physical side. But also listening and learning what Mourinho asks of us so we can do it well on the pitch."
Now entering his fourth season at the Santiago Bernabéu since joining from Fenerbahçe in 2023, Güler struck a determined tone about his ambitions for the year ahead.
"I've learned and improved a lot, but my enthusiasm has never changed. I want to win everything just like the first day and make Madridistas happy. Hala Madrid!" he said.
Real Madrid have made wholesale changes to the squad this summer under Mourinho, with the Portuguese coach bringing in Bernardo Silva, Ibrahima Konaté, Denzel Dumfries and Marc Cucurella as he reshapes the team following a trophyless campaign. Amid that turnover, Güler's improved fitness and early application in training have been read by Spanish media as a strong signal of his intentions to establish himself as a regular starter, rather than compete for occasional minutes as he did during his first three seasons in the Spanish capital.
The midfielder's own words suggest he is aware of the stakes. Having arrived as an 18-year-old with a reputation as one of the most gifted attacking talents outside Spain's own academies, Güler has spent much of his time at the club fighting fitness setbacks and rotation policy to find a settled role.
With Jude Bellingham, Vinícius Júnior and Kylian Mbappé all competing for attacking places, a strong pre-season could prove decisive in determining how central he becomes to Mourinho's plans this season.