Red Bull team chief Christian Horner was quick to warn of the threat from Mercedes after seeing Max Verstappen land pole position at the season-opening Bahrain Grand Prix.
Horner was unable to hide his pleasure, but recognised that defending seven-time champion Lewis Hamilton had made a big improvement in qualifying since the pre-season test.
Hamilton almost snatched pole before Verstappen responded with a flawless final lap to go fastest by three-tenths of a second.
It was the Dutchman's fourth pole success and set up a front row start alongside the Briton on Sunday.
"Mercedes - look at what they turned up," said Horner.
"Everyone was writing them off in the last couple of weeks and they are right there -- and they are going to be right there in the race again tomorrow.
"They are going to be a massive challenge for us to beat them, but we are starting in the best possible place."
Horner confirmed that Verstappen had damaged his car when he ran over the kerbs during qualifying.
"He smacked the bottom of the car hard. We lost a few bits of carbon. He is carrying a very small bit of damage through the session.
"You think 'oh no', but he has handled that incredibly well. He felt it, he's obviously sitting on it, but he handled that very well."