Chelsea target Hulk has scored seven goals in 12 games for Porto this season. REUTERS

Andre Villas-Boas has admitted Chelsea are in the market for one more player during the January transfer window amid renewed speculation linking Porto striker Hulk with Stamford Bridge.

The Blues are close to completing a deal for Bolton defender Gary Cahill, thought to be in the region of £7m, although personal terms are yet to be agreed.

And the Chelsea boss revealed Monday that he could sign a second player during the current window but cautioned he will not "overpay" for any potential targets.

"Apart from the central defender we might get one more player in, but we're not sure yet," Villas-Boas told Sky Sports News. "It's always difficult [in the January window]. First of all, the top talent is normally cup-tied in the Champions League, or in the different domestic competitions.

"It's difficult for the selling club to make players available. So it's normal to struggle in the transfer market.

"Normally it's a market where you overpay a lot and that's not what we want to do now. I think that's why we've set out not to do a lot in the transfer window."

One player often linked with Chelsea in recent weeks is Brazil striker Hulk. The forward played under current Blues' boss Andre Villas-Boas at Porto and has been heavily linked with a move to Stamford Bridge since his former mentor made the switch in June.

A host of top European sides - including Inter Milan and Manchester City - are also interested in the 25-year-old, but his astronomical €100m buy-out clause is likely to prove prohibitive to any January deal.

Indeed, Hulk's agent, Teodoro Fonseca, said he does not expect the player to leave Portugal this month, insisting he has not heard from Chelsea.

"The player isn't preparing to leave Porto because he is happy at the club," Fonseca told O Jogo. "I have not spoken to anybody from Chelsea. Villas-Boas knows the footballer and Porto well.

"Every day I receive calls from agents but the only serious offers we have received were three last season, offering him a better salary than at Porto.

"But Hulk rejected them because of sporting motives. He is not just interested in money but challenges on the pitch. I admit Hulk can't stay at Port forever. That is football and at the moment the clause in his deal is decisive."