Alvaro Dominguez is considering taking legal action against former club Borussia Monchengladbach for medical negligence.
The former Spanish defender this week announced his retirement at the age of 27 because of severe back problems that had prevented him from playing regularly in the last two years.
Dominguez underwent two back operations in the past 14 months and blames Monchengladbach, the club he joined in 2012 from Atletico Madrid, for not taking his medical condition seriously.
He told Marca newspaper: "I'm considering every option and I'm in the hands of good lawyers in Germany.
"The club never informed me of the seriousness of my injury. I don't need to win a court case, I just want them to recognize that things weren't done right.