Jenson Button believes that McLaren have improved significantly from Australia, but due to the characteristics of Sepang, that wasn't obvious in Malaysia last week.
Button and his rookie team-mate Kevin Magnussen both finished in the podium at the season-opener in Australia earlier this month, but failed to replicate that performance in Malaysia last week.
Before the race in Kuala Lumpur, McLaren Group CEO reported that the Woking outfit will improve by about half a second per lap after adding several upgrades to the car.
Despite that improvement not reflecting in their results in Malaysia - Button finished sixth and Magnussen ninth - the 2009 World Drivers' Champion maintained that he is confident that the upgrades would see McLaren move up the grid as the season progresses.
"I don't think we're as competitive as we were at the first race, but I think that's just circuit dependent," Button told Autosport.
"I feel that we've made a step with our car.
"We haven't done a back-to-back [test of the parts]. When you have such big parts, such big aero changes to the car, you can't just do back-to-backs.
"You waste too much time, so you've got to believe in the windtunnel.
"This year, so far everything that's come out of the windtunnel, the track has agreed with, which is great.
"I feel they [the Malaysia upgrades] have given us something, I think [Sepang] is a circuit where it's a bit difficult for us.
"The strengths of our car can't really show through.
"And the heat made those issues that we had even worse. I think with a cooler race, we'll have reasonable pace."
Eric Boullier, the McLaren Racing Director, echoed Button's comments, saying that McLaren are able to keep up in the development race with the other frontrunners.
"We are behind in terms of performance, but we know this and we are flat out on this," Boullier said to Autosport ahead of this week's race in Bahrain.
"One of the big jobs over the winter was to make sure of the correlation between the windtunnel, CFD and the track.
"What we've seen since the Bahrain tests, Melbourne and here, every upgrade we brought is matching the numbers on track, which is a good sign and a good base.
"So we just need to keep developing and keep working. We have a further upgrade coming in Bahrain and I think every race we are going to bring something."