The Portuguese outfit are trying to secure Leto's services...
The Portuguese champions have already begun looking for a left winger as Di Maria remains the subject of affection from the Blancos.
Leto, who signed for Panathinaikos from Liverpool last summer, has a contract with the Greens until 2014.
He played an influential role in the club's successful league campaign this season, but the prospect of cashing in on the 23-year-old looks too good to turn down.
"I know there is some interest and that a document is likely to have arrived at our headquarters for a first approach, but no official offer from Benfica for Leto has arrived," Panathinaikos vice-president Giannis Venkis told A BOLA.
"Negotiations are likely to start on Monday as €10 million euros are seductive."
The Argentine winger joined Liverpool in 2007 but work permit restrictions forced his way out of the club, having played a season on loan at Olympiacos before earning a permanent move to Panathinaikos.
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