After two years at Rayo Vallecano, free agent Galvez signed a three-year deal with Werder at the end of the 2013-14 season.
Galvez was reportedly attracting interesting from several European clubs, including Manchester United.
Speaking to German newspaper Bild, Galvez said he had met with German giants Dortmund but they were not prepared to trigger his release clause.
"We met in a hotel and talked about a change," said the 25-year-old, who made 26 La Liga appearances last season, scoring two goals in the process.
"I had an exit clause of €4 million but Dortmund did not want to pay for it. Then they decided to [Greece international] Sokratis Papastathopoulos."
Galvez added: "It would have been a good option, but I knew that a new one would come along. Werder is a new option."
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