Jose Mourinho has stressed Chelsea's need to strengthen their defense but hinted they may be ready to give up on Everton's John Stones.
Following the departure of Filipe Luis to Atletico Madrid, Branislav Ivanovic, Kurt Zouma, Gary Cahill, Cesar Azpilicueta and John Terry are Chelsea's only senior defenders.
It is a situation Mourinho is keen to address. The Blues have had a £17.5million bid accepted for Augsburg left-back Abdul Baba Rahman, while two offers have been lodged so far for Stones, both of which were rejected.
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Mourinho said: "Five is not enough. That's obvious.
"We cannot go to the Premier League with five defenders. That's our weakness. The quality is good, the numbers are not."
Chelsea's second offer for Stones was reported to be £26million, and Mourinho has hinted Everton's valuation of the young England international may force him to consider alternatives.
"The market sometimes has no rules. We, as Chelsea, we make our own rules," Mourinho said.
"To make our own rules is to evaluate the players, and to know the players' value, and to know when we have to stop and turn to another side, and think in another option."
Regardless of Mourinho adds to his squad in the next month, the Portuguese expects Chelsea to lose more games this season in an extra competitive Premier League.
"To win the Premier League, we don't need so many points as before," he added.
"I think more defeats, more lost points for the top teams. Crystal Palace buy (Yohan) Cabaye, as an example. I could give you much more examples.
"Welcome this mentality, welcome this economic power, welcome this ambition. If the Premier League was difficult, the Premier League will now be more difficult and I think less points will win the title."