Renault pilot Carlos Sainz Jr acknowledged that Mercedes' and Ferrari's performance in the tests was worrying him.
Mercedes was one of the most lapping teams in the test, just like it has been in recent years, and has maintained its strong performance.
Renault is expected to take a big step forward this year, and Wolff said the greatest progress could be made by the French manufacturer.
"There are not many teams that can go as fast as Mercedes, Ferrari and Red Bull with medium tires," says Sainz, who evaluates the results after the fourth day, which is a positive thing for us if we can use the tires better.
"I know it's too early, but it's no secret for anyone in Australia that Hamilton and Ferrari will be fighting for pole position.
"I think teams such as McLaren, Renault or Red Bull will be very difficult to win because the level of Mercedes and Ferrari is incredible. said.
Sainz is sure that Renault will develop.
"We are not a Mercedes or Ferrari, but I think we have a ride where we can take the steps we want."
"I do not want to set a goal, the podium is not a goal, but people have this obsession, and they want me to come out of the podium even more!"
"Maybe you'll have a podium once in the season, but overall you have not had a good year, it will be a long season and I prefer to be strong in all 21 races instead of a single podium."
The Spanish pilot admitted that he had to work hard to show the same performance as his team-mate Nico Hulkenberg.
"It will not be easy to be at Nico's level, especially I know it's fast on qualifying, but I also trust my skills."
"We were in Brazil and Abu Dhabi in 0.1 seconds, and then I was driving a vehicle I did not like because I did not develop, so I trust myself."
Asked whether he could possibly go to Red Bull, Sainz said, "This is not my dream, there's only one fellow who is going to have a good season in 2018. That will open good doors inside or outside the team."
"Right now I focus on Renault instead of focusing on Red Bull or something, they deserve it." said.