Executive director Charlie Methven confirmed last week that Sunderland had accepted a bid from the Serie A outfit, believed to be in the region of £6.6 million.
However, Ndong has been struggling to reach an agreement on personal terms and the deal now looks to be dead in the water.
Torino, managed by the former Watford boss Walter Mazzarri, are now considering other options and have been linked in the Italian press with Roma’s defensive midfielder Maxime Gonalons.
Roma signed Atalanta’s Bryan Cristante over the weekend and now have a surplus of options in the centre of the park.
Atalanta, who themselves qualified for the Europa League last season, have been linked with Ndong, as well as French side Amiens.
Sunderland are keen to move on Ndong, one of a handful of players from the Premier League era who will not see their wages reduced as a result of relegation to League One.
Aiding that process will be Richard Hill, brought in by Stewart Donald from Eastleigh shortly after his takeover was confirmed.
He is thought to be offering advice and assisting in negotiations.
The departure of those players is not essential in allowing Jack Ross to recruit new players for next season but it would clearly offer a financial boost.
Ross has the ultimate say on all incoming transfers but will be assisted by former Sunderland goalkeeper Tony Coton, whose appointment as head of recruitment was confirmed yesterday.
Coton has worked at Aston Villa, Wigan Atheltic and Bolton Wanderers and so has a strong working knowledge of the EFL market.
That was a key factor in his appointment, with Ross yet to work as a manager south of the border.
At his unveiling, Ross admitted that he would explore his own contacts in Scotland for signings but also hinted that he would want players with good experience of the English leagues.
He said: “It’s something that I’m keen to explore [Scotland] but I’m also conscious that I wouldn’t want to make it the foundations of which I build a squad.
“I think that’s something you have to be very careful of coming from another country, filling the squad with players who don’t know how to win the league you now find yourself in.
“I’d say that about the homegrown players at Sunderland too, it’s about finding the right mix that can win us this league.”
“There’s good players in Scotland. The game is a lot better than people sometimes believe.
“There’s undoubtedly players who can make that transition. the one thing if that interest becomes more concrete is that it’s not a bad sell I’ve got because it is a really big club and a really good club, and one that a player can come to and progress at.”
Ross is working on a number of transfer targets, including Blackpool’s Clark Robertson and Ross County’s Jason Naismith.
He has also been linked with a move for Peterborough attacker Marcus Maddison.