DeCastro’s knee injury may be “severe”

Steelers quarterback Ben Roethlisberger said the team’s third preseason game meant nothing.  In the end, it may mean something significant. Rookie guard David DeCastro, the team’s first-round pick in the 2012 draft, has a “potentially severe” knee injury.  That’s the official word coach Mike Tomlin provided after Saturday night’s win over the Bills in Buffalo. …