Everton may be forced to spend in the January transfer window if they are to pull themselves away from the Premier League relegation zone, according to caretaker manager David Unsworth.
The Toffees were soundly beaten 4-1 at Southampton on Sunday and are just two points clear of the bottom three.
That is despite the club spending almost £150million during the summer transfer window to bring in the likes of Jordan Pickford, Michael Keane and Gylfi Sigurdsson.
Sigurdsson drew Everton level at St Mary's with a stunning strike that cancelled out Dusan Tadic's opener for Saints - who hit back through a Charlie Austin brace and a fine Steven Davis strike.
Unsworth's run as caretaker boss has seen Everton win one of his seven games at the helm and he believes further investment may be required to turn things around.
"If it needs players who are injured to come back or January to come and go and get new players, something has to change," he said.
"This group of players is underperforming, whether it is Ronald (Koeman) in charge or me in charge it isn't working.
"There is obviously something not right going into games, on the training field everything looks right, we are getting everything we want out of them but when we go into a game situation, because our confidence is low, we are conceding far too easily."
Although he refused to accept Everton were in a relegation scrap, Unsworth did admit the coming week - against fellow strugglers West Ham and newly-promoted Huddersfield - is huge.
"I wouldn't go that far so early," he said when asked if Everton were embroiled in the relegation battle.
"I think we are in a tough moment, I think we have a massive week ahead of us. If you ask me that question next week I can give you a more honest view.
"If the players didn't know they were in a tough situation they must do now, it is evident. It is a massive week for the club."
Southampton had scored just nine league goals leading into the game but enjoyed a fine afternoon in front of goal.
Austin, who had not scored from open play since the winner in a 1-0 victory over Everton 364 days ago, was handed his first Premier League start of the season.
He said afterwards he had a point to prove but Saints boss Mauricio Pellegrino insisted he had not made a mistake leaving Austin waiting in the wings for so long.
"I decided to choose another 11, I decided other team-mates were better for those games or occasions," he said when asked about Austin's absence.
"He has trained much, much better in the last few weeks and I think he deserved his chance. You have to be ready because you never know when the manager will need you to be ready.
"Sure, I spoke with most of them but when the manager chooses 11 players it is because I feel in that moment they are right to play on that day."