Wayne Rooney made no excuses after his first game as permanent Derby manager ended in a 1-0 home defeat to Rotherham.
Jamie Lindsay fired home four minutes from time as Rotherham clinched a vital win over one of their Championship relegation rivals.
The Scot's strike saw Derby drop down to second bottom, behind their opponents on goal difference.
It was far from an ideal start to to his reign for Rooney, who pulled no punches in his assessment of his side's under-whelming performance.
"Today Rotherham outfought us," said the former England captain.
"Our quality on the ball and our concentration levels weren't where they should be.
"That's the disappointing thing and, if I'm being honest, I don't think we deserved anything from this game.
"Obviously, the preparations over the last few weeks have been hampered because of Covid but that's not an excuse for today's result.
"The lads looked good and sharp in training the last few days.
"We knew Rotherham press well and would be a tough game, but we didn't seem to have that quality on the ball.
"We seemed to lack edge and let ourselves down when in possession and under pressure.
"We know we can play better than we did today, but I don't think we even deserved a point today.
"We gave silly free-kicks away in dangerous areas and that's what Rotherham were looking for as it's a big part of their game.
"But those free-kicks allowed them to send defenders up and cause issues.
"You understand players making mistakes. But hopefully it's a one-off and we can respond properly."
Rooney's side have a chance to bounce back when they welcome Bournemouth to Pride Park in three days' time.
"The only positive from today is we play again Tuesday," he added.
"The lads know they can perform better than that today, so I expect better when we play again on Tuesday."
Rotherham's victory was their first at Derby since 1965 and boss Paul Warne said he was "really proud" of his team.
"I'm really pleased and I thought we played really well," he said.
"We put some dangerous balls in in the first half but it didn't quite drop for us.
"I expected Derby to come out stronger in the second half and raise their game and they did have a little spell.
"It looked as though it was going to fizz out into a 0-0 draw, but we were determined to come here and get a win.
"They changed their system a couple of times and fortunately for us Jamie had two bites at the cherry.
"He should have scored the first, but thankfully we managed to get the goal.
"I'm really proud of the lads.
"We've been on the wrong end of a few results lately, so it's nice for it to go our way today.
"A 1-0 away win is really impressive and the clean sheet has cheered me up no end.
"The fact we've come here and competed, the lads can be really proud of what they've done."
