Jenson Button says he feels McLaren has more to come from upgrades added to the MP4-25 at Suzuka this weekend after finishing Friday free practice in sixth place.
The McLaren driver was left to complete much of the work for the Woking-based team after Lewis Hamilton crashed out of the opening session of the weekend – an incident that also saw him miss all but the closing minutes.
Button was therefore left to run the latest-spec rear-wing on his own and despite improving the car during the day, the defending champion admitted there was still plenty of work to be done.
“This morning was pretty tricky,” he said. “I couldn't get a balance with the car at all, and was really struggling with understeer through the first sector. You give away so much time when you've got understeer through the esses because it's tougher to get the car to change direction.
“For the afternoon, we made a few changes and the car felt a lot more responsive. We're quite a bit off the pace of the Red Bulls, but we've got to look at getting the best out of the new package that we've got.
“And that requires extensive testing, which can take a couple of runs. I don't think we got the best out of our new parts, but we've made some good steps forward. We did a good job today of improving the car, but there's still more to come. That's encouraging, we're just not there yet.”