Lewis Hamilton admits he had been caught off-guard by Ferrari's resurgence but is determined to ensure their return to glory does not last long.
Hamilton was forced to settle for second place at the Malaysian Grand Prix behind the Ferrari of Sebastian Vettel as the German gave the Italian marque their first victory for almost two years.
Unlike last season when Mercedes suffered just three losses from 19 races - all of their own making due to mechanical issues - this was a "fair and square" defeat, in Vettel's words.
After a comfortable one-two in the season-opening race in Australia, Mercedes were expected to run away with this year's championship.
But it is now clear Ferrari, and their new recruit Vettel, have other ideas.
"Huge congratulations to Seb and Ferrari," Hamilton said.
"You have to hand it to them - I wasn't expecting them to be as quick as they were today, they had some serious pace and deserved the win."
Hamilton's victory bid was hampered by missing virtually all of first practice and almost 40 minutes of the second with a power unit inlet system issue.
"Ultimately I lost a lot of time on Friday, which for sure didn't help," he said.
"I ended up with a balance I wouldn't normally have. This is probably the worst balance I have had for as long as I can remember.
"Missing FP1 and a large part of FP2 really, really set us back, and me and my engineers underestimated it.
"Even so, Ferrari would have been hard to beat today, although if I had my balance similar to how I had it last year I would have made it a lot harder for (Vettel).
"But I'm already looking forward to the next race and fighting to get back to the front again."
Faster pace and better tyre management in the 30-degree heat - Vettel stopped twice for new tyres, Hamilton and team-mate Nico Rosberg three apiece - gave Ferrari the upper hand.
At times there appeared to be some tetchy moments between Hamilton and his team over the radio communication system, with the driver warning his engineer not to talk to him while he was taking corners for fear of losing control.
The 30-year-old also questioned the final tyre choice as he took on a set of hard compound Pirellis, the same as Vettel, when the quicker medium was the way to go.
Hamilton was informed, though, the only set of mediums available were already "very used", ensuring he could not fight in the final stages.
"The last few laps I realised I couldn't close down a 10-second gap," added Hamilton.
"If I'd been on the mediums at the end they wouldn't have lasted. The most I'd done on a set was 14 laps and there were 16 to go when I pitted."