Blues boss Jose Mourinho has already shelled out for Serbian football player Nemanja Matic and Bertrand Traore from Burkina Faso, while Egyptian winger Mohamed Salah will complete his switch from Swiss club Basel once he passes a medical and agrees personal terms.
Traore (18) has already been loaned to Dutch football club Vitesse Arnhem. But Salah and Matic, who returned to Stamford Bridge in a £21-million move after a spell with Portugal's Benfica club, will both be expected to contribute immediately.
Chelsea's original plan this month was to go solely for Matic, but the sales of Spaniard Juan Mata to Manchester United and Belgian Kevin de Bruyne to German Bundesliga side Wolfsburg persuaded Mourinho to splash out on the £10-million-rated Salah.
With the transfer window shutting on January 31, Mourinho says this will be the end of Chelsea's transfer dealings.
"Hopefully we are done," Mourinho said. "We are not bringing in a striker in this window."
It is a transitional period for Chelsea in Mourinho's first season back in charge in west London, yet they are still challenging at the top of the Premier League and face Turkish club Galatasaray in the Champions League last 16.
Mourinho, whose focus this weekend is on Sunday's FA Cup fourth-round tie with Stoke, said: "We would only have done Nemanja this window if we hadn't lost a player [Mata], but we are trying to keep the level and improve the squad to change the style of play.
"And we're still trying to get results and still trying to win matches … We need that mixture of young players growing up and experienced players giving stability to the team.
"We are doing that. You can see what we're trying to do. Nemanja is 26, Salah 21, so we are trying to build a team for the future.
"We're doing fine. We're calm. In relation to the domestic competitions, Man City is Man City, an unbelievable level.
"Arsenal have had eight years building this team, and this team is perfect. They're also a strong contender." – Sapa-AFP