Lewis Hamilton predicts a close qualifying session for the Australian Grand Prix on Saturday after a rain-interrupted practice on Friday.
Hamilton was second fastest to McLaren team-mate Jenson Button in the drier first practice and did limited running in the wetter second, ending up 16th.
"It looks close between us, the Red Bull, Ferrari and Mercedes," he said. "It's going to be interesting."
"I'm massively excited to see how it goes."
Hamilton added that it was difficult to predict exactly what the order would be, but said he felt McLaren were "there or thereabouts".
Button, who was 15th in the second session, added: "Red Bull are still going to be the ones to beat, but Mercedes seem competitive as well, but it's tough to say."
He added: "It is a nice way to start the season, you'd rather be first than last. A positive day.
"We didn't get a lot of running today, but it was useful because we haven't run in the wet.
"I'm reasonably happy with the car here. It feels nice, but a relatively good Friday considering the limited running."
Mercedes looked particularly impressive in the mixed conditions. Michael Schumacher said: "Today was a nice start into a hopefully exciting season, and certainly two promising sessions for us.
"However, I would not go so far as to speak about being confident, as the weather conditions were too mixed to gain a clear picture.
"We know what Friday sessions are for and don't know what fuel loads others were running. On the other hand, it is good to see that we were competitive in different circumstances today and that the car provides good handling - I just feel it."
Ferrari, who had a troubled pre-season testing programme, also looked better than expected.
Their lead driver Fernando Alonso said: "Everything went OK, positive results.
"The feeling was quite OK, and a good feeling driving the car, but I had also a good feeling driving the car in Jerez and Barcelona, but we don't know how much fuel the others had.
"It is impossible to see the level of competitiveness. There is a little bit of mix, but I am happy."