Koulibaly is understood to be a long-term target of Manchester United and they're still keen on bringing him in, according to the Mirror.
The Senegalese defender has attracted attention from all across Europe with his impressive displays for Napoli in recent years.
Napoli are understood to want around £90m for their prized asset.
United were believed to prioritise the signing of Harry Maguire last summer, which was a deal done for £80m.
Ole Gunnar Solskjaer is thought to be convinced that the 28-year-old would be the perfect partner for Maguire in the heart of United's defence.
Solskjaer's determination to bring the defender to the club is such that he has reportedly encouraged the board to make him the highest-paid player at the club.
It's unclear what such a move would mean for United defender Viktor Lindelof, who has built a partnership with Maguire this season.
United drew 0-0 with Wolves at Old Trafford on Saturday, keeping them at arm's length from Chelsea in fourth place.
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