The 25-year-old winger is reported to have fallen out of favour with coach Unai Emery and is keen to leave the Spanish club this month.
"I am looking to agree a loan transfer," Werder chief Thomas Eichin told the Weser-Kurier newspaper. "If I am to agree a loan deal, it would need to be with an option to buy.
"And if there is such an option included in a loan, then it needs to be for a realistic future simply to ensure that we have a real chance of keeping the player at our club."
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