Lopetegui made the comments following Madrid's 2-1 loss to Manchester United in the International Champions Cup Tuesday at Hard Rock Stadium in Miami Gardens, Fla. It was the team's first game since it beat Liverpool in the Champions League final on May 26 in Kiev, Ukraine.
Ronaldo bolted the La Liga power for Serie A champion Juventus on July 10. He played at Madrid's Santiago Bernabeu Stadium for eight seasons.
"What we are doing right now is taking advantage of the team we have," Lopetegui said. "We are training and working and trying to take steps forward and I'm extremely happy with the team we have."
Tuesday's roster included scores of younger players around veterans like Isco, Gareth Bale, Nacho, Marco Asensio, Toni Kroos, Karim Benzema and Kiko Casilla.
Despite Ronaldo scoring 451 goals in 438 games for Madrid, Lopetegui said that he thinks replacing the five-time Ballon d'Or winner is an "exciting task." He also said Madrid is looking to make the club even better than it was last season, despite losing the superstar.
"We have an exciting task in front of us, that's to remake and reinvent this club without Cristiano Ronaldo," Lopetegui said. "We will look to make an even better team than last year's Real Madrid. It's our task to remake this team and as I said it's an exciting responsibility what we have."
Lopetegui was asked if Bale is capable of taking the reins in place of the Portugal star, but he said he expects to fill the hole with a team effort.
"We have a great roster," Lopetegui said. "We have great players and together we will attempt to make a great team."
Lopetegui also received a vote of confidence on Tuesday from United boss Jose Mourinho. Madrid's manager was fired as coach of the Spanish national team on the night before the World Cup after he accepted the job from the La Liga power.
Critics called the move unprofessional, but Mourinho disagreed.
"I was training [managing] Inter Milan and I decided to go to Real Madrid," Mourinho said. "And because I decided to go to Real Madrid, I didn't become less professional with Inter. In fact, I played the Champions League final with Inter when everybody knew I was going to Real Madrid."
"Our choices of the future don't make us more or less professionals. When you are professional, you are professional until the last day."
Lopetegui said the "page has been turned" since his dismissal from the national squad, before thanking Mourinho for his defense.
"It's a past issue, but any defense they [Mourinho] make is good and it's appreciated," Lopetegui said.
Mourinho said that Madrid will miss Ronaldo, but the club is "bigger than any one player."
Madrid faces Juventus in its second International Champions Cup match at 6:05 p.m. Saturday at FedExField in Landover, Md. Ronaldo will not play in the bout.