Red Bull could face stiff competition just to be second best in Bahrain as Sebastian Vettel believes McLaren and Williams could get involved.
With Mercedes once again romping away with the 1-2 and Lewis Hamilton a second quicker than the chasing pack - excluding his team-mate Nico Rosberg - the race is on to complete the podium with the Merc duo.
Last time out in Malaysia it was Vettel who took the honour, finishing third behind Hamilton and Rosberg.
However, this weekend in Bahrain, the Red Bull driver believes McLaren and Williams could join him in the chase.
"[Mercedes] are very quick," he told ESPNF1. "It's not a surprise as they looked very quick in the testing here.
"I think also other teams look very strong again, McLaren and Williams at first glance. But today was just about ourselves, just like the last few weeks to be honest.
"We are trying to learn and understand more about the car and there's still a lot of progress to be made.
"I think we learned at the testing that Mercedes is very strong around this track and they have proven today they are quite quick.
"It will be a long way for us to catch up but in the long term it's important for us to make bigger steps than them. Today was a good, solid day for us."
Pressed as to whether Red Bull could mix it up with the Mercs, the reigning World Champion ruled out the possibility.
"That would be very soon, it's only one week. It's very difficult to say where we are in terms of pace but it's very easy to say we are not with Mercedes."
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