"I'm going day by day. If I'm thinking about calls and my future, I wouldn't be able to enjoy being with the national team," Reguilon told Radio Marca.
"Obviously, Real Madrid is my home, but it's not easy... I'm bearing everything in mind."
Real Madrid won La Liga in 2019-20, breaking a run of two consecutive titles for Barcelona. Though third-place Atletico Madrid and Sevilla both finished 12 points behind runners-up Barcelona, Reguilon still believes the gap is closing between the top two and the rest of the league.
"Each year, things are getting a bit more equal, although Real Madrid and Barcelona are still the best," Reguilon said.
"It could be the case that Sevilla compete for La Liga and that'd make me very happy."
Reguilon has admitted that he'd like to be a part of a potential title-challenging Sevilla side, saying he has developed a close bond with Lopetegui.
"He means a lot to me and I have a lot of love for him," Reguilon said of the manager who gave him his Real Madrid debut during his time in charge of the Blancos in 2018-19.
"He gave me my first opportunity in professional football and now we've shared something very special.
"When I saw him crying after winning the Europa League, I couldn't have been happier for him. He worked like a madman."