The 21-year-old centre-back has impressed in La Liga this season and has a release clause of just €12 million.
Atletico have spoken to both Salisu and his club over a potential transfer, although sources at Valladolid insist that no formal offer has been made.
Five Premier League clubs have made inquiries, with at least three of them lodging serious interest in the defender. La Liga side Valencia have also made contact.
"Salisu has been a sensation in La Liga this year," Juan Mata Sr. told VIP Deportivo this week. "Playing as a centre-back at that level isn't easy. I think this could be his window, because there has been interest from many clubs, and he deserves it."
The biggest challenge facing Atletico in completing a deal is their delicate financial situation, with the club having been hit particularly hard by La Liga's suspension amid the coronavirus pandemic.
Last month, Atletico had to implement a cost-saving ERTE, with the squad taking a 70% pay cut, and players and directors contributing to make sure other employees did not lose out on wages.
Even a modest €12m fee would represent an obstacle, and Atletico would look to reduce that sum by offering academy players to Valladolid in part exchange. The Spanish club would be also willing to allow Salisu to remain at Valladolid on loan for another year before joining manager Diego Simeone's squad in 2021.