Boga, 23, first joined Chelsea's academy in 2009 but left the club in 2018 having failed to break into the first team, managing a single senior appearance for the west Londoners.
His form has been good since moving to Sassuolo for £3.5 million around 18 months ago, with 10 goals and five assists in 50 appearances. Representative Daniel Boga told GianlucaDiMarzio.com his brother remains on Chelsea's radar
"In December I met with [Chelsea director] Marina Granovskaia. She's following his season with great interest. There are no concrete offers, but there's strong interest. Barcelona asked me for information. I spoke to others but many clubs want him. Napoli? Certainly, but many called from France and England. I'm very proud of this growth. For many it's a surprise, but certainly not for me. His future is at a top club."
Goal's Nizaar Kinsella reported the value of Boga's alleged buyback clause, which could allow Chelsea to re-sign the player for less than his market value:
Boga has scored seven goals and recorded four assists in 22 Serie A appearances for Sassuolo this season, more than doubling his previous career-best for goals in a single season (three).
His form has spiked in recent weeks with a run of three goals and two assists in his last four league appearances, including a sensational long-distance equaliser when Sassuolo beat Torino 2-1 in January:
He more recently scored and assisted in a tense 2-1 victory over Serie A strugglers SPAL on Sunday when he decided the match with an injury-time header:
The winger was farmed out to Rennes, Granada and Birmingham City on successive season-long loans between 2015 and 2018, racking up a combined 92 appearances for the three clubs.
Boga has flourished in a Sassuolo side engineered to fit his attributes. His brother added that they were "convinced immediately" after Edo Crnjar—agent of Sassuolo manager Roberto De Zerbi—sold them the project they envisioned at the Stadio Citta del Tricolore.
Chelsea already have a number of wingers in the squad, including academy graduate Callum Hudson-Odoi, and there's no guarantee Boga would be willing to settle for a deputy role after thriving in Italy.
The Blues may not pass up their opportunity to re-sign a blooming talent for a modest price, though it appears Boga could have other elite options in front of him come the end of this season.