Boss Ronald Koeman is said to rate the 24-year-old highly and is keen to add another centre-back to his squad before the transfer window closes.
Koulibaly, who joined the Italian giants from Metz last summer, has struggled to adapt to life in Italy after making just 14 appearances for the club.
Spanish daily Estadio Deportivo are reporting that Arsenal are about to pounce for Sevilla midfielder Grzegorz Krychowiak.
The La Liga side are said to be concerned that the Gunners will trigger his £21.4m release clause.
Liverpool are about to confirm the departure of striker Fabio Borini.
The Guardian say Borini will move to the Stadium of light after being frozen out at Anfield under Brendan Rodgers.
They also report that Sunderland are also working on a deal for United winger Adnan Januzaj.
Everton manager Roberto Martinez has vowed John Stones will not be leaving the club during the transfer window period, despite interest from Chelsea.
The England centre-back has been the subject of intense speculation over a move to Premier League champiions with the Blues launching three big-money bids in attempt to land the young England international (TalkSport).