The Blues’ miserable season continued with a 2-0 defeat by Everton at Goodison Park on Sunday, and Pochettino has made it clear that he is not happy with the level of his squad, despite the club spending over £1billion on new players under owners Todd Boehly and Clearlake Capital.
Pochettino said the first four months of the season have been a “reality check” that requires Chelsea to “do something” to meet expectations at the club.
It remains to be seen how Pochettino’s comments will go down with the Stamford Bridge hierarchy, but his job is not thought to be under immediate threat, despite Chelsea languishing in 12th place in the Premier League after an underwhelming campaign so far.
Pochettino will hold talks with co-sporting directors Paul Winstanley and Laurence Stewart, and potentially owners Boehly and Behdad Eghbali, about January transfer plans.
The Argentine on Sunday identified a lack of aggression and a lack of goals as two key problems which need to be addressed, and it is understood he wants to target a defender, a central midfielder and a striker next month.
He believes his squad is imbalanced and a lack of height is an issue, with the Blues having the second smallest squad in the Premier League.
Chelsea signed 12 players at a cost of almost £400million in the summer, but have managed just five wins from their first 16 League matches.
After another disjointed display on Sunday, Pochettino said: “After four or five months and 16 Premier League games, it is [time to] assess.
"If we are not capable today with all the chances that we had — we need to score if we want to be in a different position in the table. If we are not aggressive enough, maybe we need to do something, some movement.
"That is something to analyse with the sporting directors and the owners and see what we can do to change this dynamic and change in the second part of the season.
“Expectation was massive. For Chelsea, the expectation is always to win the Premier League, but after is the reality. Sometimes it is a good, a reality check. We need to fight. Mid-table is our reality now.
"If we want to go up, it is not only to play well, it is about being more tough with ourselves. We are going to push the players, the players need to push themselves, and then it is a massive assessment from the beginning of the season to today, and when the transfer window opens, see what we can do.
“I’m not saying we need to ask for more players or less players, but it is to see if the perception matches the reality. If expectation is here (high) and reality is here (low), it is because we are missing something in the middle. Maybe we need to improve our reality.”
"We are missing something... we need to improve our reality"
Mauricio Pochettino on Chelsea's transfer need
Injuries to captain Reece James, defender Marc Cucurella and goalkeeper Robert Sanchez compounded a bad day on Merseyside.
James came off with another hamstring injury, while Sanchez suffered a knee injury and Djordje Petrovic came on for his Chelsea debut in the second half.
James only recently returned after two months out with a hamstring problem and is set for scans this week amid fears he is set for another spell on the sidelines.
His fitness issues are becoming a real concern for Chelsea and injuries could yet impact on their transfer strategy in January. Chelsea are confident they can spend more and stay within Financial Fair Play rules, but may look to sell Trevoh Chalobah and Ian Maatsen.