I once had a friend who took an interest in vexillology, so much so that he actually bought a set of flags. By the time they arrived he realized he didn't have the room or the means to actually do much with the flags, so he used them as tablecloths.
Carlos Silva is a flag in this case. The Mariners really didn't need him and they really didn't have the means (read: defense) to use him. The only difference between the flag and Silva is that Silva can't be used as a tablecloth; otherwise he will eat your food without remorse.