Playing Until the End by Stephanie Queen

A Sizzling Sports Romance Superstar NFL quarterback Trent Lockheed is aging out of the only life he's ever known. This is his last chance to reach his goal of getting into the hall of fame. But he needs a boost to do it. When he hears about Dr. Charline Morneau's research trial on a promising new serum, he wants in. Charlie Morneau will do anything to fund the research on her serum because it could help save her mother and sister's life. She would even agree to allow the secret participation of a professional athlete in her drug trial. Trent and Charlie make an unholy secret deal that could get them everything they want--or that could cost them more than they realized they had...