Carrie Prejean and NFL Husband Take Big Loss On Mansion

Kyle -- who quit the NFL this summer, ONE DAY after signing with the Chargers -- purchased the 4,322 square-foot house in 2008 for $2.55 million ... two years before he met Carrie.

Prejean was added to the home's deed when she got engaged to Boller in 2010.

But, after owning the house for several years, the couple decided it was time to go ... and unloaded the 4-bedroom, 4-bath crib last month for $2.35 mil -- way below what Kyle paid.