Source: DeCastro is expected to miss 3-5 months

We’ve gotten some clarity regarding the knee injury suffered by Steelers guard David DeCastro.  And it’s not good. Per a source with knowledge of the situation, DeCastro is expected to miss three-to-five months with various injuries in his right knee.  Though the official diagnosis will come via a Monday MRI, we’re told that DeCastro currently…