Unless he got the number wrong, Clob mentioned 56 at center. That's Shack. And he's been out since last Friday. A day before that, IT said:
Zach Shackelford has been a topic the last couple of days with growing concerns he'll be able to hold up versus Notre Dame. To this point the staff doesn't seem overly concerned, but the freshman center is struggling with both the upperclassmen across from him as well as some of the freshmen. Both quickness and power are giving him issues.
This is similar to what Clob was saying.
He also mentioned 68 (Brandon Hodges) as struggling which is NO surprise at all, along with 77 (Patrick Vahe). Patrick just moved from the right to the left side for Fall Camp - he was still at RG in the spring - so his struggles aren't that surprising as he's only a sophomore.
So, if it's true that Clob was at practice last week, maybe he'll see some real improvement on his next visit. We can always hope.