ULSTER (7th) v OSPREYS (2nd), Ravenhill, 7.05pm (live BBC 2 Northern Ireland)
Team News: Head coach Brian McLaughlin has named Paul Marshall and Pedrie Wannenburg in the Ulster starting line-up for their RaboDirect PRO12 showdown with the Ospreys.
Marshall is included at scrum half, with versatile South African Ruan Pienaar moving to out-half and Ian Humphreys dropping to the replacements bench.
Pienaar has played in the number 10 jersey for his previous club Natal Sharks, as well as for the Springboks. The Ulster back-line remains otherwise unchanged from the one that faced the Cardiff Blues last weekend.
Up front, Wannenburg has returned from a foot injury and will pack down at number 8 in place of the benched Robbie Diack.
Chris Henry will again captain the side from the blindside flank, with Willie Faloon remaining on the other side of the scrum.
Dan Tuohy and Lewis Stevenson continue the partnership in the second row. There are two changes in the front row with Paddy McAllister coming in at loosehead prop for Callum Black and Andi Kyriacou replacing Nigel Brady at hooker.
There are still tickets available for Friday's game. They can be bought online at www.ulsterrugby.com or by calling the ticket office on 02890493222. Alternatively, you can pay at the gate on match night.
Meanwhile, centre Stefan Watermeyer will make his RaboDirect PRO12 debut for the Ospreys, replacing the benched Ashley Beck in the number 12 jersey.
Watermeyer's inclusion is one of two changes to the back-line that the Welsh region fielded against Aironi last time out. Rhys Webb also makes way for Samoan international Kahn Fotuali'i at scrum half.
In the forwards, Scott Baldwin makes his first league start at hooker alongside the returning Duncan Jones. Ian Gough has been added to the second row and London Irish-bound flanker Tom Smith continues as captain
The Ospreys are missing 16 players who are away on international duty with Wales, Ireland, the Wales Under-20s and Scotland Under-20s.
A decision will be made regarding Jonathan Thomas' fitness before kick-off, as he recovers from the back injury that meant he missed last weekend's win over Aironi.
ULSTER: Stefan Terblanche; Craig Gilroy, Nevin Spence, Paddy Wallace, Ian Whitten; Ruan Pienaar, Paul Marshall; Paddy McAllister, Andi Kyriacou, John Afoa, Lewis Stevenson, Dan Tuohy, Chris Henry (capt), Willie Faloon, Pedrie Wannenburg.
Replacements: Nigel Brady, Callum Black, Adam Macklin, Tim Barker, Robbie Diack, Ian Humphreys, Simon Danielli, Adam D'Arcy.
OSPREYS: Richard Fussell; Hanno Dirksen, Andrew Bishop, Stefan Watermeyer, Eli Walker; Dan Biggar, Kahn Fotuali'i; Duncan Jones, Scott Baldwin, Joe Rees, Ian Gough, James King, Tom Smith (capt), Sam Lewis, Joe Bearman.
Replacements: Mefin Davies, Ryan Bevington, Will Taylor, Jonathan Thomas/Lloyd Peers, George Stowers, Rhys Webb, Matthew Morgan, Ashley Beck.
Referee: Neil Hennessy (Wales)
Assistant Referees: Dudley Phillips, Sean Gallagher (both Ireland)
Television Match Official: Kevin Beggs (Ireland)
Match Odds (Paddy Power): Ulster to win: 1/4; Draw: 22/1; Ospreys to win: 3/1
Pre-Match Quotes: Brian McLaughlin (Ulster) - "A lot of players - and I mean a lot of players - were slipping off tackles (against the Cardiff Blues) and that is an area Jonny Bell has looked at this week.
"We also gave seven penalties away when we had possession, and if you are doing that then you do make life difficult for yourself.
"Yes, there were times when I thought we were harshly done by, perhaps more so in that similar offences by Cardiff were missed, but that is the way it was and you just have to take these things on the chin.
"As far as the league is concerned every game is a must win, but the games ahead of us now are all crucial given that we must win if we are to give ourselves the best chance of staying in the mix.
"We were exceptionally disappointed with the way we played last week and I expect a reaction to that this week. We started well enough last week, but we just could not get any continuity going and we either turned ball over or we were penalised."
Jonathan Humphreys (Ospreys) - "It's good to go to Ulster off the back of two wins, but we know that there's going to have be a real improvement from last week if we are going to make it three from three.
"Ravenhill is always a difficult place to go, even more so when they are in the kind of form they've shown during their European campaign this season.
"It's likely to be a full house, a passionate atmosphere, and a difficult evening for what is largely a young Ospreys team, with a sprinkling of experience.
"It's nights like these where you learn a lot about a team, about the character and spirit of young guys. It's going to be a great test.
"We've got ourselves in a good position in the PRO12, mainly down to these guys, who've been here during the World Cup and Six Nations. We need to maintain our focus now and make sure we finish the job in the coming weeks and secure that home semi-final."
Top Scorers - 2011/12 RaboDirect PRO12: Ulster - Points: Ian Humphreys 100; Tries: Darren Cave 4; Ospreys - Points: Dan Biggar 138; Tries: Rhys Webb 4
RECENT LEAGUE MEETINGS:
Friday, April 3, 2009 - Ulster 13 Ospreys 16, Ravenhill
Saturday, September 12, 2009 - Ospreys 16 Ulster 20, Liberty Stadium
Tuesday, April 13, 2010 - Ulster 27 Ospreys 38, Ravenhill
Friday, September 3, 2010 - Ulster 27 Ospreys 26, Ravenhill
Sunday, February 13, 2011 - Ospreys 23 Ulster 22, Liberty Stadium
Sunday, September 25, 2011 - Ospreys 32 Ulster 14, Liberty Stadium
- Ulster's three-match winning run in the RaboDirect PRO12 ended at the Arms Park against the Cardiff Blues last Friday
- The Ulstermen's only defeat at Ravenhill in their last 17 matches in all competitions was a 23-12 loss to Benetton Treviso on October 7
- The Ospreys have won three of their last four encounters in the RaboDirect PRO12. The Welshmen have won all six fixtures they have played against Irish opposition so far this season
- The Ospreys have won their last two games against Ulster and have won at Ravenhill on four occasions in the league (only Leinster have done as well in Belfast)