Andre Villas-Boas has revealed he could sign two players in the next few weeks but warned that Chelsea will not overpay in the transfer market this month.
The London club have had a bid accepted by Bolton for England defender Gary Cahill, but personal terms are still proving a sticking point.
Speaking at Monday's William Hill Scottish Cup draw in Glasgow, Villas-Boas said: "Apart from a central defender, we might get one more player in but we're not sure yet."
He added: "It's always difficult. The top talent is normally cup-tied in the Champions League or in different domestic competitions and it's difficult for the selling club to make players available.
"It's normal that you struggle in the transfer market.
"Normally it's a market where you overpay a lot and that's what we don't want to do now.
"That's why we have set out not to do a lot in the transfer window."