Heikki Kovalainen believes Red Bull look set to continue their Formula One dominance in 2011.
Although Sebastian Vettel and Mark Webber did not set too many headline times at Valencia and Jerez, Team Lotus driver Kovalainen said the underlying speed of the new RB7 car was apparent.
"They seem to have everything under control. It is my feeling that they have not yet shown even half of their full ability," the Finn is quoted by Turun Sanomat.
But the 2008 Hungarian GP winner also thinks Ferrari will have a say in the outcome of the 2011 championship.
"Similar to Red Bull, Red Bull have a strong feeling about them. Williams also did a very good laptime in Jerez.
"With McLaren it's still difficult to say," said Kovalainen, who drove for the British team alongside Lewis Hamilton for two years.
"They came a bit late to the tests and they have had some problems, but at least their car is good looking, it may well be fast," he added.
Kovalainen is more worried about the Mercedes team.
"The body language I have seen tells me that they are disappointed with the car's performance," said the Finn, referring to Michael Schumacher and Nico Rosberg.
As for Team Lotus, Kovalainen said the "difference to the top (cars) has definitely been lessened.
"The (T128) car feels good in every way. (1982 world champion) Keke Rosberg said our car looks like it belongs in Formula One now," he smiled.
"He is right. But we have to remember that we are only a year old, while Red Bull took 6 or 7 years before they started to win. We have a long road ahead," said Kovalainen.