The 32-year-old full-back, who used to play for the likes of River Plate and Metalist Kharkiv and has been capped for Argentina, is making the noble sacrifice for his sibling who has cancer. Villegra is expected to be away from training until early March.
"I am the only compatible family member," the defender told regional Argentine radio station El Deportivo 12.
"I've been doing research for three-four months and I'm compatible with my brother, you never think you would go through one of these situations.
"I will try to help him as much as possible. As a donor it fills me with pride and makes me feel very good. It is difficult to ignore the issue of my brother's illness. It affects me being a close relative and it's not easy, everyone in the club knows that.
"They supported me and gave me words of encouragement, I only have words of thanks."
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