Hamilton started the race in fourth following a disappointing qualifying session where both Ferrari’s were considerably quicker.
During the race itself, Mercedes’ lack of speed was clearly visible as second-placed Valtteri Bottas finished almost nine seconds behind winner Daniel Ricciardo, of Red Bull.
Hamilton, who is out of contract at the end of the season, is still searching for his first win of 2018.
But if performances do not improve in the foreseeable future then the decision to pen an extension with Mercedes may be a difficult one.
The Brit has been in negotiations over a new deal since the turn of the year and he has previously admitted he will only sign an extension if he is given a chance to win the world championship.
And now Hamilton has claimed that he might not even have the second fastest car on the grid, never mind the first.
The 30-year-old feels Red Bull and Ferrari are quicker – sparking worries that he could walk at the end of the season.
“Who knows what this season holds, but if it continues this way it is going to be very tough to win the championship,” Hamilton said.
“We under-performed in qualifying and the race was a disaster on my side of the garage.
“It has not changed my thinking about the season, and my goals are obviously still the same, but it is clear from this weekend that we are not the quickest.
“We are the second or third fastest team at the moment so we have got some improving to do, but that is not impossible.
“I’ve got to take it upon myself to try and figure out what has gone wrong and move forward.”