Fulham vice-chairman Tony Khan has apologised to the club's fans for their start to the season and has promised to sign new players.
The Cottagers have lost their three opening league games - conceding 10 goals - including Monday's 3-0 home reverse by Aston Villa.
Fulham were promoted via the play-offs but have only brought in two new first-team players on permanent deals.
"I promise players in and better efforts from this squad," Khan tweeted.
Full-backs Antonee Robinson and Kenny Tete were the permanent summer arrivals in Scott Parker's squad against Villa, while goalkeeper Alphonse Areola, who started on Monday, was one of three loan signings.
Fulham's central defenders have been error-prone in their opening three games - only West Brom (this season) have ever conceded more in their opening three games of a Premier League season.
"We've looked to add centre-backs since Wembley," Khan explained. "I'm sorry we haven't [signed any] yet as two got Covid, we lost a free we thought was close and had another issue with a fourth centre-back.
"I should and will apologise repeatedly for that performance. I'm sorry everybody. We all need to do a better job.
"Everyone at the club for the past year worked really hard to get the team up and now we need to work significantly harder to stay up. I promise better efforts than today."
Fulham spent over £100m in the summer of 2018 when they were promoted from the Championship, and went straight back down. Parker, who finished that season in charge, led them back to the Premier League at the first attempt.
He told BBC Sport: "We can keep working and try to improve but I think it's clear to everyone what we need to do. Whether that's on the training ground or in the market, that's what we're going to do.
"I said from the outset [after promotion] and when we sat down with people at the football club - I know where we were and where we are now.
"It's going to be a tough year, we're going to face a tough challenge and we need to work out if we want to compete in this league or just be a passenger."
On whether he thinks he will be able to add to his squad, he said: "Hopefully. Bringing in players is difficult. Let's see come the end of the window."
The transfer deadline for signings from Premier League or foreign teams is next Monday.