Sporting have received an enquiry from Nottingham Forest for centre-back Ousmane Diomande.
Sources in Portugal say they have received expressions of interest from the Midlands club for the Ivory Coast international, 22, but they have stopped short of an official bid.
Diomande is known to have a £68.2m release clause in his contract but could be available for less this summer.
Multiple sources say new Forest manager Oliver Glasner is driving any potential move and was keen on signing Diomande when previously in charge of Crystal Palace.
Diomande has made more than 150 senior first team appearances despite his age, including 15 appearances for his national team and an appearance at the World Cup this summer.
He was also previously a target for Chelsea and reportedly linked with a host of other clubs in Europe.
Forest have yet to make any signings having narrowly avoided relegation to the Championship last season but have sold midfielder Elliot Anderson for £116m and David Carmo to Olympiacos for an undisclosed fee.
