Jenson Button said Sebastian Vettel could still be caught in the drivers' championship and vowed to "fight until the end" to catch the German.
Red Bull's Vettel has won five of the first six races this season and Ferrari's Fernando Alonso believes he has "nearly" won the title.
But McLaren driver Button said: "There's so much that can still happen.
"We could all just give up now and not bother, or we could fight until the end, which is what we're going to do."
The Briton added: "It's swings and roundabouts. He could get very unlucky for the next few races, so we're not going to give up."
Vettel's victory in Monaco on Sunday took him to 143 points, 58 clear of McLaren's Lewis Hamilton, who is second in the standings.
Red Bull's Mark Webber is third on 79, Button fourth with 76, and Alonso fifth on 69.
The last man to make such a stunning start to the season was Button in 2009 when he won six of the first seven races with Brawn GP.
However, Button's form dipped, other teams caught up with the pace and he only just held on to take the title in the penultimate race.
The big difference, though, is that Red Bull have a billionaire owner behind them in Dietrich Mateschitz, while Brawn was run on a shoestring.
"We didn't have the resources, and we weren't really willing to spend the money," added Button on the situation two years ago.
"So we had a great car at the start of the year, but we didn't keep it throughout the year, and these guys will.
"They've had a very quick car for two years now, so it's going to be difficult."
Alonso, who was second in Monaco, said Vettel's blistering start had put him on the verge of the championship, despite there being 13 more races this season.
"We saw in the last couple of years that if you win five or six grands prix you've nearly won the championship," said the Spaniard.
Asked how he could close the 74-point gap that now separates him from Vettel in the drivers' championship, Alonso pointed out that even with the new scoring system, under which the winner of each race receives 25 points, he would need to win three races and Vettel not score at all.
"I think at the moment it's not possible," said the Spaniard.
"If you are one second behind in every qualifying and you have to do some strange strategies, so some starts or something always out of the normal race [to try and win], it's difficult.
Alonso suggested Ferrari may now target podiums rather than wins.
"Victory for us is maybe optimistic, so we need to be realistic and start fighting for podiums in Canada and Valencia and then we will see how the championship develops, because... the distance now is too much."
Asked how he rated Vettel's performance at Monaco, Alonso it was "fantastic".
He added: "Not only today, winning five races in six grands prix. There's only one occasion that happened a couple of years ago with Jenson [Button] in the same situation and we know Jenson's result: winning the championship."