The Blues will be hoping to keep up the trend of the last six meetings between these two teams in the Magners League which have all been won by the home side on the day.
The Ospreys' only previous win at the Arms Park was a 15-9 success on January 1, 2005.
New Year's Day will see the Scarlets welcome Newport Gwent Dragons to Parc y Scarlets in Llanelli.
The Dragons have won just four of their previous 13 encounters with the Scarlets, and have been victorious in Llanelli just once - in September 2007.
So the hosts will be hoping to build on the success of their last home game which saw them secure a 27-13 victory over Cardiff.
The second leg of the league's Scottish derby will take place at Firhill Arena on Friday afternoon with Edinburgh taking a 33-point lead from the first game between the two on December 26.
That fixture smashed the record crowd for a Magners League game in Scotland (12,534), so the Warriors will be looking for a good turnout at Firhill to break their attendance record as well.
In Ireland, Connacht will be looking to build on their historic win over Munster by completing a first ever 'season's double' over a fellow Irish province when they travel to the Dublin to face Leinster.
This will be a difficult task for them given that Leinster have been beaten just once at the RDS since October 2007.
The Ulstermen's last win in Munster was a 20-17 triumph in Cork on December 3, 2005. Their last success at Thomond Park was over 16 years ago, in the Interprovincial Championship on November 28, 1992.
MAGNERS LEAGUE ROUND 9 FIXTURES:
Wednesday, December 31:
Cardiff Blues v Ospreys, Arms Park, 2.05pm (live Setanta Sports Ireland/Setanta Sports 1/BBC Wales)
Thursday, January 1:
Scarlets v Newport Gwent Dragons, Parc y Scarlets, 5.15pm (live Setanta Sports Ireland/Setanta Sports 2/S4C)
Friday, January 2:
Glasgow Warriors v Edinburgh, Firhill Arena, 3pm (live Setanta Sports 1)
LEINSTER v CONNACHT, The RDS, 7.30pm (live Setanta Sports 1 and 2)
Saturday, January 3:
MUNSTER v ULSTER, Thomond Park Stadium, 7.30pm (live Setanta Sports Ireland)