Besiktas hope to sign Buttner on loan by the end of the week.
"During the [friendly] match against Sevilla in the past weekend, interest was expressed," Buttner's agent Aleksander Bursac told Renascenca Radio.
"He put in a good performance. There was interest from Benfica to sign a defender, but that news is already history.
"Two days later, Benfica confirmed to me that they would keep the two left-backs [Melgarejo & Cortez] that they have left the squad.
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