The backrower is one of four changes made by Director of Rugby Phil Davies as the Blues look to continue the fine European form which saw them secure back to back Heineken Cup wins over Glasgow Warriors.
Davies also recalls centre Dafydd Hewitt with Rhys Patchell missing the game through injury. Gareth Davies continues at fly half while the return of Pretorius sees Macauley Cook move to lock to partner Filo Paulo.
Prop Benoit Bourrust is named in the front row alongside hooker Kristian Dacey and skipper Sam Hobbs. Rhys Williams, Scott Andrews, Josh Navidi and Gavin Evans are all named amongst the replacements.
Davies said: “We face an Ospreys side packed full of international talent and who have impressed this season to currently lie in fifth place in the table, just two points off a play-off berth.
“They also secured a big European scalp last week against Castres so will arrive full of confidence. We need to be ready to meet that challenge.”
While the Ospreys will no doubt be tough opposition, the recent form of Davies’ side is a confidence booster. The Blues are in second place in Pool 2 of the Heineken Cup, two points behind defending champions Toulon.
“We are looking to build and improve on the form that has seen us secure some important results over the last two months,” Davies added.
“We are under no illusions as to the size of the task that awaits us but it’s an exciting way to finish 2013 at the Arms Park.”
While the Blues have impressed in Europe, the Ospreys have had just the one victory, albeit an impressive home triumph over the current French Top 14 champions. Boss Steve Tandy recalls skipper Alun Wyn Jones at lock while there is also a welcome return for Wales tighthead Adam Jones.
“This is the first game of a busy five weeks with three big derbies followed by the final two rounds of the Heineken Cup,” said Tandy.
“Christmas is a great time for rugby. It’s about the tradition and the rivalry and it’s fantastic for regional rugby in Wales that we are going to have a series of games with big crowds and great atmospheres.
“We are looking to build some momentum after showing some good signs in the games against Castres. The win last weekend was a great result for everybody involved with the region, but there is still plenty of room for improvement.
“It’s important we are at our best in Cardiff in front of a big and passionate crowd. We know there’ll be a large travelling support and we want them to be proud of what this group is doing.
“If we can keep the momentum going and put in the kind of performance they expect, we’ll be in a good place before back to back games against the Scarlets.”
