And River are expecting an offer to arrive from Leeds – but Betis could get involved.
The Andalusian club are planning to back new coach Manuel Pellegrini in the transfer market.
And two-time Argentina international Martinez Quarta is in their sights as part of a squad rebuild.
There is talk that Betis could offer $12m (€10.2m), far from the player’s $22m (€19.3m) release clause.
But River need cash and would consider a $12m offer to be ‘attractive’ enough to consider.
Agent: “In the next few days…”
Martinez Quarta’s agent Gustavo Goni confirmed interest in the player, adding that no specific offer has yet been made.
“If what the media said was true, we would have already sold him several times,” Goni told TyC. “You have to be patient, this has just started. No club was going to be thinking about signing him while playing important games.
“I think in the next few days the wheel will start to turn and we will see where things stand then.”
In addition to Spain and England, Goni said Martinez Quarta would also be interested in the French and Italian leagues.
Martinez Quarta has made 96 appearances for River Plate and the feeling is he is now ready for a big European move.