Real Madrid midfielder Toni Kroos has admitted it will be "difficult" for the European champions to replace the 50 goals a year that Cristiano Ronaldo all but guaranteed playing up front for the club.

Ronaldo scored 450 goals in 438 games during his nine seasons at the Bernabeu before joining Juventus this summer, finishing as top scorer in the Champions League as the club won four of the last five trophies.

Despite links to potential replacements including Paris Saint-Germain's Neymar, Bayern Munich's Robert Lewandowski and Inter Milan's Mauro Icardi, Madrid's only attacking addition this summer has been €45 million Brazilian teenager Vinicius Junior.

Speaking to kicker after being named Germany's Player of the Year, the former Bayern Munich midfielder said Ronaldo had been "instrumental" in Madrid's recent successes but he remained "absolutely convinced" in his team's chances for the new campaign.

"We'll see about that," Kroos said. "It'll be difficult to compensate 50 goals per season. Cristiano has been an important cornerstone for us in the past years, and was instrumental for our successes. In spite of that I am absolutely convinced of our team. We will again be hard to beat this term."

Toni Kroos and Cristiano Ronaldo won three consecutive Champions League together at Real Madrid Getty

This summer saw Madrid's other leading playmaker, Luka Modric, win the Golden Ball as he led Croatia to the World Cup final, then speculation that the 32-year-old could be set for a surprise move to Inter Milan.

Kroos did not comment on the possible transfer, but did say he had not been surprised by Modric's performances during the tournament in Russia.

"It's clear that I believed this was possible," he said. "We've been teammates for four years now -- I know what an incredible player Luka is."

Kroos said it had been "exciting" getting to know new Blancos coach Julen Lopetegui during their International Champions Cup campaign in the U.S. through recent days.

"I've been in training for a week now and it's exciting for me since I didn't know the coach before," he said. "He makes a highly motivated impression. And my Spanish colleagues only said good things about him. I am looking forward to working with him."

Lopetegui has now added to his coaching staff by hiring former Spain under-21 coach Albert Celades, with the pair having worked together closely through recent years with the national federation.

A former Barcelona youth team graduate who spent four seasons at Madrid in the early 2000s, Celades would be very useful at the Bernabeu, Lopetegui said: "[Celades] will help us a lot in the work of preparing the team, in all we do on and off the pitch. We are delighted to add him to our coaching staff."