History may favour the visitors, but Connacht have a good home record and success over the champions would be a welcome prize.
Elsewhere, the Newport Gwent Dragons will be looking for their first ever victory on Leinster soil when they travel to the RDS in Dublin.
Four of the top five teams are in action on Sunday. The third-placed Cardiff Blues entertain Ulster, who are currently lying fifth in the table, while current table toppers Munster face the second-placed Scarlets at Musgrave Park.
A bonus point win for the Scarlets could knock Munster off the top of the table for the first time since the opening round. A five-point return for Ulster would see them retain the play-off spot they held before the round started.
However, both those scenarios would require away victories, and points are always harder to pick up on the road.
Friday, November 19 -
CONNACHT v Ospreys, the Sportsground, 7pm
LEINSTER v Newport Gwent Dragons, the RDS, 7.05pm (live RTÉ Two)
Sunday, November 21 -
Cardiff Blues v ULSTER, Cardiff City Stadium, 3.45pm (live S4C)
MUNSTER v Scarlets, Musgrave Park, 5.35pm (live TG4/BBC Wales)