Brittney Griner spent nearly 10 months imprisoned in Russia before her release on Dec. 8. (Christian Petersen/Getty Images)

Brittney Griner took to social media Wednesday to thank her fans for their support and to advocate for fellow American detainee Paul Whelan.

Griner was released earlier this month from Russian custody after being swapped for convicted arms dealer Victor Bout. She had been imprisoned since February for the alleged possession of hashish oil and sentenced to nine years in a Russian penal colony.

Throughout her detainment, many WNBA players, fans and more wrote letters to Griner, advocating for her release through the We Are BG campaign.

Every letter “mattered,” she wrote Wednesday.

“You took time to show me you cared and I want to personally take the time to write to you and say that your effort mattered,” she wrote. “Your letters helped me to not lose hope during a time where I was full of regret and vulnerable in ways I could have never imagined. Thank you, from the bottom of my heart. Because of you I never lost hope.”

The letters, Griner wrote, “were also bigger than uplifting me.”

“They showed me the power of collective hands. Together, we can do hard things,” she continued. “I’m living proof of that. My family is whole and now, thanks to you, we are fortunate to get to spend the holidays together.”

The Phoenix Mercury star, who has said she intends to play in the WNBA this upcoming season, added that there “remain too many families with loved ones wrongfully detained.”

“Those families stood alongside you and all supported the We Are BG campaign to bring me home and it’s our turn to support them,” she said, urging her supporters to write to Whelan, who remains imprisoned in Russia.

Whelan has been detained in Russia since December 2018. U.S. officials have said that they are still negotiating for his release, but Russia views his espionage charges differently than Griner’s drug charges.

“I hope you’ll join me in writing to Paul Whelan and continuing to advocate for other Americans to be rescued and returned to their families,” Griner said. “Thank you again from the bottom of my heart. I hope your holiday season is full of joy and love.”