This is one instance where rumors actually turn out to be true.
A few weeks ago, there was speculation that Frank Grillo would be in Captain America: The Winter Soldier.
Grillo will be playing the role of Crossbones, a nemesis of Captain America.
Tidbit: In Fallen Son: The Death of Captain America, Crossbones is actually responsible for killing Captain America, but I highly doubt Marvel will go with this plot in the upcoming sequel.
The film will be in theaters on April 4, 2014.