The two players may end up moving clubs in separate transfers rather than as part of a swap deal.
Celtic's interest in Sunderland Steven Fletcher, and the Wearside outfit's own pursuit of defender Virgil van Dijk may have to occur in separate transfers, according to the Sunderland Echo, rather than the swap deal mooted in the media.
Sunderland are said to be just one of the sides tracking the talented Dutchman, with the likes of Southampton, Everton and Arsenal also linked to the 23-year-old according to the Echo.
So on the surface of that interest, many would have thought that Celtic's own chasing of Scotland striker Steven Fletcher would make a deal involving each player heading the other way, an attractive proposition.
However, the Echo have stressed that there are complications regarding a deal involving both players, with a more likely resolution being that Sunderland pay big money for Van Dijk to secure his signature on its own.
The former Groningen star made a massive 58 appearances for the Bhoys last season, scoring 10 goals as Celtic won the league for the second time since he arrived, as well as the League Cup.
Fletcher nearly joined Celtic when he left Hibs in 2009, before heading to England with Burnley. But the forward has just 12 months remaining on his contract, and the Black Cats are already set to make a big loss on the 28-year-old, with him having scored just 8 times in the last two seasons.
The Scottish champs may see Fletcher as worth significantly less than the £10 million they are said to value Van Dijk at, and look to recruit him in a separate deal or at the end of his contract.