Ken Rosenthal of FOXSports says the Mets are shopping Luis Castillo.

The Mets are again expressing a willingness to trade Castillo, and the team has contacted the Colorado Rockies.

The problem is Castillo’s contract. Castillo is guaranteed $6 million this season and $6 million in 2011. If the Mets and Rockies agreed to a trade, the Mets will likely have to pay almost all of that money.