Ferrari were the quickest in pre-season testing in Barcelona with Red Bull's RB13 fourth, behind champions Mercedes and Williams.
Verstappen feels Red Bull can improve as the campaign progresses but he doesn't think they will be able to match the likes of the Scuderia and the Silver Arrows in the season opener in Australia next weekend.
"We still have to wait and see how good we really are," Verstappen told De Telegraaf.
"Personally, I don't think we can fight for the win at the moment.
"Much can change during the course of the season, but we are not good enough yet to win."