The Spaniard has made just 33 league starts for Liverpool since he joined from Espanyol for £8m in September 2008.
Riera, 27, has featured less this season than last term and has been pushed even further down boss Rafa Benitez's pecking order by the arrival of Argentine star Maxi Rodriguezback in January.
A source for Villarreal said: "If a deal for Riera is feasible, we will have to explore our options."
Former Gunner Pires, 36, is set to leave El Madrigal at the end of the season after four years at the club as his current one-year deal comes to an end - and Riera is seen as the ideal man to replace him on the left flank.
Sevilla are also interested in bringing Riera, who had a loan spell at Manchester City in 2006, back to his native Spain.
go la.
hanor, i dont even know why is he here?
cos he is spanish
he's just on the field to make up the needed 11 players
go go go