Harry Maguire says England's defenders may have been affected by their poor club form during Friday's defeat to Czech Republic.
Goals from Jakub Brabec and Zdenek Ondrasek overturned the Three Lions' early lead as they went down 2-1 in a Euro 2020 qualifier in Prague.
England's back line consisted of Tottenham left-back Danny Rose, Everton's Michael Keane and United centre-back Maguire, who are all enduring difficult spells with their clubs in the Premier League. Meanwhile, right-back Kieran Trippier has played consistently with his new club Atletico Madrid, though he has not experienced a win with them since the start of September.
And Maguire acknowledged that their struggles at club level may have crept into their performance for the national team.
The 26-year-old was asked if he and his team-mates were low in confidence heading into the game and replied: "Yes, maybe. We bring our club football into international level. It was a difficult game. Don’t get me wrong, we started sloppy. We took the lead in the game but we didn’t deserve to.
"In the second half we controlled the game a lot more than the first half but we gave them a sloppy goal to win the game. We do need to improve on that. We were not at our best and got punished for it."
While the defender conceded that it takes time for the squad to jell, he urged his team-mates to adapt to the demands of international football.
“You are wanting to develop partnerships," he added. "Sometimes in international level you can’t really do that.
"You have players who aren’t playing for their clubs so they don’t get selected, and you have players that pick up injuries.
“You’ve got to adapt. That’s one of the tricky parts of playing international football. Every camp you’re normally playing alongside [someone new] – you don’t want to be – and need to develop new partnerships.
"But listen, there’s no excuses. [The defence] need to be better. We need to be better going forward. We need to be better on the ball. And we certainly need to be better at keeping the ball out of the net.”
The former Leicester star was disappointed with the way England conceded against Friday's hosts.
Brabec's equaliser came from a corner less than five minutes after Harry Kane opened the scoring, while Ondrasek capitalised on Jordan Henderson's attempted pass to Rose.
"The first goal was a set-play and we probably need to tighten up on those," Maguire said. "We’ve been really good over the last year or so at defending set-plays.
"The second goal has come from us being a bit too open when we were trying to build up from the back and maybe it was at a stage of the game when we shouldn’t have looked to do that.
"We could have consolidated the point and tried to play in their half a bit more. So maybe better game management would have helped us, at worst, draw the game 1-1."