The club have yet to sign a direct replacement for the Portuguese superstar, who switched to Juventus in July after scoring 450 goals in 438 games over nine seasons at the club.
“Instead of asking who will score those goals we need to challenge ourselves by scoring more than that as a team,” Lopetegui said.
“The whole team will have to score all those goals (that Ronaldo scored) between them. Score more goals and concede less of them.”
Madrid boast Welsh winger Gareth Bale, French striker Karim Benzema and rising 22-year-old Marco Asensio in their forward line but have just five days of the current Spanish transfer window left if they are to buy a new striker.
Some reports have said Real are waiting to see if they can lure World Cup sensation Kylian Mbappe away from Paris Saint-Germain.
“It would be useless to put that terrible pressure (of replacing Ronaldo) on one person, it would be a sword of Damocles,” Lopetegui said.
“We have a wonderful squad and I'm delighted with all of them because I can see they are ready to give everything to win the league and all the other competitions,” he said.