Jenson Button believes McLaren could have challenged the two Mercedes cars if his race wasn't ruined by a pitstop.
Starting Sunday's Malaysian Grand Prix seventh on the grid, Button found himself in fifth place behind the two Red Bulls and two Mercedes cars for most of the afternoon.
However, all his hard work was undone when a mistake during his third stop saw him leave his pit box with his front right wheel not attached. He managed to rejoin the race after the mechanics pushed him back and attached the wheel, but he was way too far back to stand any chance of finishing in the top 10.
He eventually retired with three laps left as the team looked ahead of the Chinese Grand Prix.
Button, though, believes he had enough pace to give Lewis Hamilton and Rosberg, who finished third and fourth respectively, a run for their money during the latter stages of the grand prix.
"It's easy for me to say we would have been on the podium as we didn't finish and I am sure a lot of people will disagree with me, but I think we had a chance to fight with the Mercedes," he told Sky Sports F1.
"We had one less pitstop to do, but I don't know what would have happened, but I think at worst it would have been fifth. We could have pushed the Mercedes and they were fighting between themselves so it could have been interesting."
Although Button didn't pick up any points, it was a solid weekend for McLaren as they have improved in qualifying and in terms of race pace following their troubles in Australia last week.
"It is a good improvement over the last race just a week ago," he added. "We never thought we would be fighting for fifth, let alone a little bit better, so there are positives, but it is always very tough when you have an issue like this as it is a lot of points to throw away - even fifth is 10 points. So that is tough, but the positives are that we are improving and I can see that we will be even more competitive in China."