It's no secret that DeCastro and fellow rookie Mike Adams were struggling in camp. We saw Adams picked apart by the Philadelphia Eagles in the preseason opener and DeCastro, according to reports, hadn't exactly dazzled coaches.
Despite the sluggish start, DeCastro and Adams represent a youth movement along an offensive front that couldn't protect quarterback Ben Roethlisberger a season ago. Outside of center Maurkice Pouncey, this line has been degraded by age and average play.
Teams rarely use a first-round pick on a right guard, but the Steelers fell hard for DeCastro, whose play at Stanford made him one of the Pac-12's most consistent linemen last season. When they grabbed Adams in the second round, Pittsburgh's restocked line became a storyline of the summer. Now they're spinning their wheels again.
Fourth-year lineman Ramon Foster is expected to step into DeCastro's spot, which is no upgrade. Foster started 13 games on the right side last season and one on the left, part of a unit that fielded five different starting combinations over the first 10 games of 2011. Line coach Sean Kugler is well-respected, but he has his work cut out for him all over again.
A tough break for a team that hopes to keep Big Ben happy -- and upright -- for 16 games.
UPDATE: DeCastro could miss as much as three to five months, according to Mike Florio of ProFootballTalk.
Follow Marc Sessler on Twitter @MarcSesslerNFL.