Police say that 67-year-old Enrique Guzman suffers from Alzheimer's and has been missing since Wednesday.
Guzman was last seen at a gas station in his blue Chevy Camaro.
Winslow is asking anyone who sees his father-in-law to contact Anaheim police.
Winslow, a Pro Bowler in 2007, was a first-round draft pick out of Miami in 2004 by the Cleveland Browns. He was traded to Tampa Bay after last season.