Jenson Button says he is bracing himself for a 'tough' Russian Grand Prix, despite a better than expected qualifying session on Saturday.
The Briton will start from 13th on the grid at Sochi – which is his second best performance of the season after qualifying 12th (but starting 10th) in Monaco.
But despite the positivity of the pace in getting through to Q2, Button fears that the long straights at Sochi will again expose the big weakness his Honda engine has in terms of energy deployment.
"We performed okay, probably a touch better than I personally felt we would," he said.
"Tomorrow though is going to be a very tough day. I think a difficult day for us with the weaknesses we have.
"It will cost us quite a bit of laptime in the race."
When the energy deployment on the McLaren's Honda engine runs out, Button and Fernando Alonso find themselves without the 160bhp the boost gives them.
That is why they are often overtaken by their fully powered rivals before they get to the braking zone.
Button confessed that the situation at Sochi would likely be as bad as it had been in recent races.
"It will be an issue and whatever we do on lap one, can be undone very easily," he said. "So it is tough in that situation.
"We are both very emotional when it comes to racing, and we are passionate about racing and we want to do all we can, even if it is fighting for 13th. You want to do all your can to keep the cars behind you.
"We will do all we can tomorrow and use everything in the right way in terms of deployment and what have you. But it will be a tough day.
"It is definitely not going to be any easier than Suzuka. We will do our best and see where we end up.
"We can't use strategy either because it is very unlikely that people will be doing a big amount of stops tomorrow."