Sporting CP want to turn Pedro Porro's loan from Manchester City into a permanent deal.
The Spain international joined Sporting at the start of the season on a two-year loan.
The deal included a buyout clause of €8.5 m.
And Goal says Sporting want to activate the clause.
Porro has missed only one league game this season, with Sporting enjoying six point buffer on top of the table.
The Lisbon-based giants are hoping to win their first league title in 19 years.