Mauricio Pochettino has suggested Chelsea must consider spending in the January transfer window, saying his side "are missing something".
Chelsea fell to back-to-back defeats for the first time under Pochettino when Everton handed them a 2-0 loss at Goodison Park on Sunday.
The result leaves Chelsea 12th in the Premier League, 18 points off leaders Liverpool and 10 above the drop zone after 16 matches.
- Everton 2-0 Chelsea - Report and highlights
- Premier League table | Watch free Premier League highlights
- Stream the Premier League and more with NOW | Get Sky Sports
That is despite Todd Boehly and Behdad Eghbali spending more than £1bn on players since they oversaw the takeover from Roman Abramovich in May 2022. Under Pochettino, the club recruited 13 players at a cost of more than £400mi in summer.
But asked whether Chelsea need further reinforcements next month, Pochettino said: "It's about improving. We are talking after four, five months - 16 games - and it's about assessing.
"If we are not able to score today with all the chances we had… we have to score if we want to win the game.
"We want to be in a different position in the table. The team played well against a very difficult team like Everton. We were much better than them but you need to score.
"After the first half of the season, we need to check. That is the reality. If we are not receiving enough, maybe we need to do some movement.
"That is the thing to analyse with the sporting directors, to see if we can change this dynamic and improve in the second half of the season.
"We need to be more aggressive. Then it's a massive assessment and when the transfer window opens, we will see what we can do.
"I don't say if I am going to ask for more or less players. It's to see if the perception matches the reality.
"We are missing something. We need to improve our reality."
James, Sanchez, Cucurella all added to injury list
Chelsea have suffered a large number of injuries throughout the season, with 10 first-team players unavailable for the trip to Everton.
Christopher Nkunku and Romeo Lavia are yet to make their debuts as they continue to recover from long-term injuries, while vice-captain Ben Chilwell is also sidelined.
Captain Reece James suffered another hamstring injury at Goodison Park, while Robert Sanchez and Marc Cucurella also had to be replaced.
"I don’t like to talk too much about excuses but this is the reality with one of the best full-backs in the world," Pochettino said of James. "We will assess in the next few days what is going on with his hamstring.
"Sanchez suffered a problem against Manchester United, an issue with his knee. He felt something during the second half [against Everton]. That’s why he asked for the change.
"We hope that it’s not a big issue, like Marc Cucurella, who twisted his ankle.
"From the beginning we are dealing with these situations and it’s too much. It’s a young team and we need everyone together if we want to build something solid."