Australian Daniel Ricciardo won for Red Bull in Shanghai last year, from sixth on the starting grid, and while that team has switched from Renault to Honda power they remain competitive.
Ricciardo has moved on to Renault, but Max Verstappen was third in the season-opener in Australia and fourth in Bahrain two weeks ago.
"You definitely can’t count them out," Hamilton told reporters on Thursday at a cold and overcast Shanghai circuit.
"They’ve had a bit of a slower start but I think if you look at last year for example, they won the race here and they particularly finished strong.
"I anticipate it could be something similar."
Hamilton has had more success around the 5.4 km track than any other driver and champions Mercedes have enjoyed one-two finishes against the odds in the first two races of the season.
While the 34-year-old would usually arrive as favourite for the win, especially in the V6 turbo-hybrid era with Mercedes having won all but one race in China since 2014, all bets are off this year.
"It’s only the third race," said the five-times world champion.
"Obviously we didn’t expect the performance we had at the first race, we didn’t expect to see what we saw at the second race. I don’t really know at the moment."
Pre-season favourites Ferrari were surprisingly off the pace at Melbourne’s Albert Park.
They were then fastest in Bahrain but it was Hamilton who inherited the victory after an engine problem some 10 laps from the finish denied Charles Leclerc an easy maiden win.
"I hope that we don’t have to rely on reliability, and I hope we have a much closer race," said Hamilton.
"This is a great track to have a real race, so the closer it is the better."
Ferrari’s greatest strength in Bahrain was straight line speed, with Mercedes team boss Toto Wolff estimating their advantage at 0.5 seconds down the straights alone.
That could give the red cars an edge, with the Shanghai circuit's main straight over a kilometre long.
(Editing by Alan Baldwin/Toby Davis)
