Kimi Raikkonen has played down mounting speculation about Alfa Romeo's ability to be a dark horse of 2019.

His former Ferrari teammate, Sebastian Vettel, on Wednesday singled out the ex Sauber team as a notable standout of winter testing.

Now working closely with Ferrari, the 2019 Alfa Romeo was designed by former Ferrari designer Simone Resta, and has caught attention with its innovative front wing and other experimental details.

"The car feels good, fast," Finn Raikkonen confirmed to Germany's RTL.

"However in F1, all the cars are fast. Even the slowest ones," he added.

But Raikkonen, now 39, is not known for giving away much to the media. For instance, when asked to divulge something about his 2019 car, he answered: "It is fast."

As for the difference between the Alfa and last year's Ferrari, Raikkonen said: "The rules have changed and this has an effect on how the car looks and behaves, but so far the car has worked well.

"The first race will show us where we are compared to the others. Right now it's just guesswork."

Former F1 driver turned British television pundit Johnny Herbert told Ilta Sanomat newspaper: "It's still early, but Alfa Romeo seems to have a strong car.

"Ferrari was obviously more focused on Seb, and I think Kimi's character is such that he didn't try much to change that.

"But now Alfa looks good and Kimi seems to have more energy," Herbert added.