Andre Villas-Boas admits Chelsea are in talks with Bolton Wanderers to sign centre-back Gary Cahill during the January window.
The Blues boss indicated that his club have held 'initial' discussions with Bolton over the 26-year-old, as the Portuguese looks to strengthen his central defence.
However, Villas-Boas suggested he has alternative plans if a deal for Cahill cannot be worked out.
"Regarding what we are trying to do in central defence, we are trying to close a deal [for Gary Cahill] but I don't think we will do much more than that, maybe one more player," the manager told the club's official website.
"Central defence is our number one priority and we will try to solve it as soon as possible.
"We had initial talks with Bolton but that doesn't mean he is our only target."
Villas-Boas also updated the injury status of Branislav Ivanovic and midfielder Jon Obi Mikel.
The versatile defender was injured in the Boxing Day draw against Fulham but looks set to return sooner than Mikel, who also picked up a knock in the match.
"Ivanovic will be back sooner than Mikel," Villas-Boas said.
"We are looking at the Portsmouth game for Ivanovic and it is not impossible for Mikel either but it might be a bit too soon."
Chelsea host Aston Villa on New Year's Eve at Stamford Bridge.