It turns out that the "mystery player" that was referenced in the fanshot below was DT Willie Williams, who signed with the Eagles today.

The 6-4, 305 lb Williams is a 2nd year player out of Louisville who spent time on the Rams' practice squad last year.

Since Jeremy Maclin is still not in camp, the Eagles didn't have to cut anyone to add Williams to the roster. When Maclin does sign, Willie may very well find his stint with the Eagles short lived.