Middlesbrough defender George Friend admitted his side looked 'lethargic' during their 2-0 defeat by Nottingham Forest.
Boro missed the chance to go top of the Championship after losing their first game at the Riverside this campaign.
Second-half goals from Joe Lolley and Lewis Grabban saw Forest, managed by former Boro boss Aitor Karanka, take all three points, and Friend admitted the performance fell well below his side's usual high standards.
"We've set a really high benchmark and we need to get back to that," Friend told MFC.com.
"Its hard to put a finger on what went wrong today, but first half I thought we were second to everything and looked a bit lethargic.
"[Forest] took confidence from that, the goal made a big difference and we were chasing it a bit.
"Every week in this league you need to be at it and be the fighting team.
"They have good quality and they took their goals well but we have to be better."
Boro boss Tony Pulis will now have two weeks to mull over a performance he described as 'a bag of potatoes'.
The Teessiders slipped to fourth ahead of next week's international break, but Friend insisted his side aren't looking at the table after just 12 games.
"It would have been nice to go into the international break top and I keep talking about our standards and that's where we want to be," the defender added.
"But we know it's very close and there's a long way to go.
"We're not going to put our heads down and mope about but we know we've got to be better than that as well."