Sebastian Vettel has admitted he thinks Mercedes could be struggling.

While the 2019 pecking-order may be muddied, the general consensus is that Ferrari is leading the pack.

"I have not analysed the times so much," Vettel, after crashing the 2019 Ferrari in Barcelona, said.

"But I think we should be good. Red Bull looks very strong and consistent, and reliable so far.

"There could also be a few surprises," the German added. "Alfa Romeo, for example, looks very good."

As for Mercedes, the dominant world champion since 2014, Vettel admits the German team may be struggling.

"It's a bit difficult to read what's going on," he said. "Some runs look good, others less so."

But Vettel admitted he was "a little surprised" to see the extent of Mercedes' aerodynamic upgrade for the start of the second Barcelona test.

"But everyone chooses their way. And it only really starts in Melbourne anyway," he said.