Button: More to come from upgrades

The reigning champion struggled in first practice at Suzuka and was only 12th. He felt McLaren made a lot of progress in the afternoon, although he admits that Red Bull currently looks to be out of reach.

"This morning was pretty tricky, I just couldn't get a balance with the car at all," said Button. "Really struggling with understeer through the esses, and you give away so much time when you've got understeer there and a lazy front end. I also had an off on high fuel, which was interesting.

"This afternoon we changed the car quite a bit and it was a lot more responsive, so I'm much happier with the car this afternoon. But still we're quite a bit off the pace of the Red Bulls. But I think we've just got to look at getting the best out of the package we have.

"I think today we did a good job of improving the car, but there's still more to come. We know the areas, which is good, we're just not there yet."

He said the need to thoroughly evaluate McLaren's upgrades had masked the car's full potential today.

"The parts that we're putting on the car need testing and it takes up a couple of runs," Button explained. "But I don't feel that we're on the back foot. I still don't feel like we've got the best out of the parts that we have on the car, but the positive thing is we made some good steps forward today.

"The only thing is, I think tomorrow's going to be wet, so it's a very different situation to today. But this has been very useful work for Sunday.

"Everything we've put on the car makes the car go quicker, so I'm happy with that. But we're still not getting the full potential, and we have to tomorrow. We've changed the car a lot today and it's been better, so it's going in a good direction."

Button thinks McLaren is already well prepared for the wet based on its form in other damp events this year.

"We have a very good car in the wet, so we've just got to make sure we don't veer too far off the path of what we've done before in the wet," he said.

He denied that his team-mate Lewis Hamilton's crash in practice had put McLaren at a major disadvantage by limiting how much work it could do on its upgrades, while acknowledging that the loss of track time had not helped.

"Obviously it's better to have two cars on the circuit, you get a lot more information," said Button. "It's a pity, but I almost did the same thing myself. We got a lot of useful information and hopefully that's enough for Sunday."