Editor's Update: Per NFLN's Ian Rappaport, David DeCastro did tear his ACL. The initial report we ran did not suggest this was the case. Schefter's report came via Twitter at 12:07 p.m. CT, and Rappaport's came via Twitter at 12:09 p.m. CT. Rappaport has noted via Twitter he's checking with his source again. Schefter has not Tweeted since his announcement.
Update: Rappaport Tweeted he was "misinformed," and confirmed Schefter's report that David DeCastro did not tear his ACL.
Per Schefter, DeCastro tore his MCL, which was previously reported, dislocated his knee cap and suffered some damage to his patella tendon (knee cap), but the ACL itself is still intact.
Steeler Nation breathes a sigh of relief, but DeCastro's return this season is still undetermined. What the MRI results do confirm is he will miss at least a few games, and missing the whole year is still a possibility.
If he is able to return, the length of time he'll need to return will depend largely on his rehabilitation process. It wasn't reported, but these injuries are not typically ones requiring surgery. The lack of mention in the initial report suggests surgery will not be necessary.
DeCastro was injured in Saturday's 38-7 preseason win over Buffalo. He left on a cart, and Steelers coach Mike Tomlin initially suggested it was a "severe" injury, and all things considered, it seems like it could have been worse.