Chelsea have seen a £30m bid for centre-back Alessio Romagnoli rejected by AC Milan, according to Sky in Italy.
It is understood the Serie A club do not want to sell the 21-year-old Italy U21 international in this window.
Romagnoli joined Milan for £21m last summer from Roma, making 34 starts in the Italian top-flight last season, and the country's press have even compared him to some of the great Milan defenders such as Alessandro Nesta and Thiago Silva.
After his side won 2-1 at Watford on Saturday, Chelsea head coach Antonio Conte stressed the need for a new defender at the club.
"If you look now at our squad, we have only five defenders - four that started today and an academy player Ola Aina," said Conte.
"Ola is very good - he has great potential - but with any young player you must work to put them in the first team. Sure, he has a good future.
"If one defender is injured or banned, then we are in trouble, but the club and me we know this and we are talking every day to improve the squad.
The Blues had targeted Napoli's highly-rated centre-back Kalidou Koulibaly, but Sky Italy reported on Monday that he was set to stay at the club.