Australia paceman Mitchell Starc bemoaned his team's execution as England closed in on Ashes victory on Friday.
With the tourists bowled out for 60 in the first innings at Trent Bridge, England declared at 391-9 before leaving Australia 241-7 at the end of day two.
Australia are on the verge of going down 3-1 in the series, and Starc said they had simply underperformed throughout.
"When you're playing at your best... I think we haven't seen that from us," he said after taking 6-111 in the first innings.
"We saw that at Lord's I guess, which was up there with as good a performance as we can do. Since then, execution just hasn't been there and England has been up to the challenge.
"They've played good cricket and haven't given the momentum back to us when they've taken it. We definitely haven't played anywhere near our best cricket."
Despite being close to giving up the Ashes, Starc said his hurting team would continue fighting.
"I think it's disappointing as a group, whether it be no runs on the board or not bowling enough in certain games as well. We're sticking by each other," he said.
"I think we probably could've bowled a bit better yesterday also, so we probably leaked a few too many runs, which comes with trying to take wickets and attacking a bit too much.
"It's been a couple of disappointing days for us, but we'll come out tomorrow and give it another crack."