Daniel Ricciardo admits he was impressed by Ferrari's pace at Jerez, but is confident Red Bull will close the gap in Barcelona.
The Italian outfit set the pace on three of the four test days last week with the Ferrari-powered Sauber claiming top honours on the other day.
Red Bull, meanwhile, struggled with reliability issues and Ricciardo and team-mate Daniil Kvyat completed only 164 laps compared to the 500 plus from Mercedes and Ferrari's 346.
The Australian, though, believes we will get a clearer picture at the second test at Barcelona.
"[At] the first test you try to just worry about yourself, but of course we're aware of what Mercedes did, and the lap time Ferrari put down. It looked good," he told the Australian Grand Prix podcast.
"We expect nothing less of Mercedes to be honest, but Ferrari looked like they came out pretty strong.
"For now they look good, but it's one of those things. It's still early, and Jerez is a place that A, we don't race at, and B, we never drive in conditions that are like five-to-eight degrees. And the track is really, really abrasive there; the tarmac is a lot more aggressive than any other track.
"So they look good, but are they going to be the same once we start racing? I think Barcelona will get us a step closer to that, and then we'll see where we are.
"But I'm not taking anything away from them; I think they've come out in good form."