The Cardiff Blues are looking to rebuild their fortress at the Arms Park and have won their last three games at the venue, but last season's European champions, Leinster, will be tough opponents.
The Scarlets sit just outside the play-off positions, and any points they can take off their visitors Connacht, who do not have a very good record in Wales, will be welcomed.
Ulster took over at the top of the table after round 5 and have remained there ever since. They have now pulled out an 11-point lead which could stand them in good stead during the international period.
The last game on Friday night is at Rodney Parade where the Newport Gwent Dragons host Benetton Treviso. The Italian outfit have a good record against the Dragons, but the men of Gwent have picked up positive results in their most recent games outside the league.
The two Scottish teams both face away trips, Edinburgh to Munster on Saturday and Glasgow Warriors face Zebre in Italy on Sunday.
Victory over another Italian side, Treviso, in the last round lifted the Warriors into second place in the table, the highest position they have held all season.
Conversely, Munster's loss at home to Cardiff saw them drop out of the play-off zone. With just four points separating the second to sixth-placed teams, the challenge for the top four spots is really on.
RABODIRECT PRO12 - ROUND 14 FIXTURES:
Friday, February 8 -
ULSTER (1st) v Ospreys (4th), Ravenhill, 7.05pm (live BBC 2 Northern Ireland/BBC 2 Wales)
Cardiff Blues (7th) v LEINSTER (3rd), Cardiff Arms Park, 7.30pm
Newport Gwent Dragons (11th) v Benetton Treviso (8th), Rodney Parade, 7.30pm
Scarlets (5th) v CONNACHT (10th), Parc y Scarlets, 7.30pm
Saturday, February 9 -
MUNSTER (6th) v Edinburgh (9th), Musgrave Park, 7.45pm (live TG4/BBC ALBA)
Sunday, February 10 -
Zebre (12th) v Glasgow Warriors (2nd), Stadio XXV Aprile, 3.05pm local time (live SportItalia/BBC ALBA)