Jenson Button admitted he was concerned by the gap to the front of the field after qualifying fifth at Hockenheim.
The world champion outqualified his McLaren team-mate Lewis Hamilton, but was only fifth - and 0.7 seconds down on front row pair Sebastian Vettel (Red Bull) and Fernando Alonso (Ferrari).
"I don't know where seven tenths is. That's the worry I have," said Button. "For me it was a good lap and I don't think there was anything else I could've got out of the car. To be seven tenths behind is a little frustrating."
He is certain that McLaren has made gains in recent rounds, but it has still been leapfrogged by Ferrari and lost a little ground to Red Bull.
"We've definitely made a step forward," he said. "The car feels good around here. It's just not enough in qualifying spec. Hopefully tomorrow we'll see some more performance in the car."
Button had no complaints about the newly-introduced blown diffuser.
"I think it's working well, it's just not enough compared to the Red Bulls," he said. "We've definitely made a step forward for this race, but it's still a big gap."
He still hopes to make progress towards the front in race trim.
"It's a pretty fun circuit here to race on, and the first lap's always pretty hectic, so we can have a great race," he said.
But he added that while he was perturbed by his car's deficit to its main rivals, he did take some satisfaction from improving his personal qualifying performance after trailing Hamilton by several places in recent rounds.
"It's the best lap I've done for a couple of races," said Button. "I needed to do a reasonable job in qualifying this time - and I have."