Lewis Hamilton and Valtteri Bottas fear Mercedes will be watching Ferrari "disappear" at the Chinese GP given the straight-line speed the Scuderia showed in Bahrain.
Ferrari were clearly faster than Mercedes at the Bahrain GP with pole-sitter Charles Leclerc nearly four tenths ahead of Hamilton, who started third in the desert.
On race day, Hamilton and Bottas were able to secure Mercedes' second one-two of the season after Leclerc's late engine problem and Sebastian Vettel's spin.
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However, both Silver Arrows drivers think Ferrari will hold the advantage again in Shanghai, which boasts the second-longest straight on the F1 calendar.
"If they have this straight speed in the next race then we'll be watching them disappear," said Hamilton after his win in Sakhir.
There are suggestions that Ferrari gained as much as half a second on the straights in Bahrain.
Asked if he was worried by the Shanghai International Circuit's straight, Bottas replied: "Honestly it does, yes.
"We have seen [in Bahrain] Ferrari was making all the time on the straights and in China there are even longer straights. So we do need to work on [things]; for sure we are improving the car all the time and we have to review what we can do for the straight lines.
"It's going to be tough but we showed [on race day] if we keep focusing on ourselves and not other things, anything is possible."
Mercedes are the most successful team at the Chinese GP, having won the race on five occasions. Bottas also led last year's race until an untimely Safety Car left him at the mercy of Daniel Ricciardo's charging Red Bull, with the Finn having to settle for second behind the Australian.
Ferrari have not won in China since 2013 but locked out the front row last year before Sebastian Vettel was also caught out by the Safety Car and then hit by Max Verstappen when running third.
Mercedes completed 178 laps during the in-season test in Bahrain last week and while rain and a water leak did not enable them to complete their planned programme, they managed "the important bits and leave with more information and understanding of the car and tyres" and "managed to test some developments that we plan to roll out over the next few races".
Bottas feels Mercedes' best hope of closing up to Ferrari is managing to find more time in cornering.
"The next two races, China and Baku, have massively long straights. I think [in Bahrain] Ferrari were making more than four tenths only in straight lines per lap," he said.
"We can't find four tenths like this, we need to maybe try and find it in the corners and some of it in the straight line. It's early on in the season, there is a long way to go, but at least we know what we can still work on."
Watch the Chinese GP, F1's 1,000th race, live on Sky Sports F1 on April 12-14. Sky Sports is the home of live and exclusive F1. Find out more here to watch the 2019 season live