One key, and often overlooked, part of Sarri's side is their defensive record. So far Chelsea have conceded just three goals this season, something which has only been bettered by Jürgen Klopp's Liverpool.
However, Sarri is keen on bolstering his defence even further in January, according to Calciomercato, with Milan pair Romagnoli and Caldara being lined up in an audacious move by the Chelsea boss.
As well as being tipped as the future of Milan's defence, the two fully-fledged Italy internationals are also believed to be the most likely players to succeed Giorgio Chiellini and Leonardo Bonucci in the long term for the Azzurri.
If Sarri is serious about luring both Romagnoli and Caldara away from San Siro when the transfer window opens then the Italian will face a huge uphill battle for their signature, as the ball is certainly in Milan's court.
Romagnoli signed an improved four-year contract at the end of last season and there is no need of Milan to cash in on their star defender, while Caldara only joined during the summer after being used to sweeten another deal which saw Bonucci return to Juventus.