Vice-captain Callum Whelan admitted Carlisle United fell below their standards after losing away to Eastleigh on Saturday afternoon.
The midfielder returned to action after a spell on the sidelines but was left frustrated by a performance he felt saw the Blues lose too many battles across the pitch.
He said: "I think we were second best in every department. You can have whatever formation [or] system you want, but I think we lost too many duels, too many 50-50s and it's just not us.
"It's not what we speak about every day, every week. First things first is we outrun the opposition, we outfight them before we think about any in-possession stuff or any system tactics, and we didn't today.
"I think we lost battles all over the pitch and we weren't good enough."
Whelan believes United moved too far away from the fundamentals that have underpinned their performances so far this season.
"I think sometimes you can get mixed up. We're a team that wants to dominate the ball, of course we are, and we want to be attacking and on the front foot, but you can't forget about the fundamentals that earn you the right to play and win your football matches, and it's simple.
"Heading, tackling, running, talking, way too quiet today.
"Just didn't really turn up."
The midfielder says the squad now needs to reflect on the performance and ensure they respond positively in the week ahead.
"There's got to be a lesson. The game's got to be a lesson in terms of we can't let that happen again.
"We've got fans over there that have travelled the length of the country, staff, yourselves. All this way to not really show up is not good enough at all.
"We've got to get in on Monday, work harder than we did last week and yes, we've got to get better."
