Hudson picked up his 5th yellow card of the season at Ewood Park and misses the match on Saturday against the Championship's bottom club.
It's a real Goliath v David clash with Championship leaders City going for an 11th straight win at home. Quite a superb run of form.
Either Peter Whittingham, or more likely Craig Bellamy, will captain the side.
When asked who it would be Malky Mackay said:
“I won’t rush into that one and will wait a few more days before deciding,” said Mackay. “Losing Mark for the Peterborough game is a massive blow.
“He has been captain fantastic since day one of my time in Cardiff. He leads by example, scored another goal at Blackburn and had to be brave when the home team pumped high balls into our penalty area.”
Rookie Ben Nugent could step in for Hudson or more likely Matt Connolly will move inside with Kevin McNaughton returning after injury.
Tommy Smith could also be in contention for a place in the squad after several weeks out injured and Jordon Mutch is available after suspension for City's last home game before Christmas.
Cardiff v Peterborough
Saturday 3:00pm.