HARRY O'Brien will miss Collingwood'scrucial clash against arch-enemy Carlton with an ankle injury. 

The defender has been burdened by his anklefor the past fortnight, and has had several scans.  

Club doctors have decided to give the26-year-old a week off and will the reassess his progress. 

While the Magpies hope O'Brien will missjust one match, it could be more. 

Full details of the teams for theblockbuster will be released from 6.25pm on AFL.com.au. 

MattThompson is a reporter for AFL Media. Follow him on Twitter @MattThompsonAFL