There are two changes to the Ulster side that battled to an away win over Bath in the last round of European action. Best comes in for Nigel Brady at hooker, and the fit-again Stephen Ferris returns at blindside flanker.
Robbie Diack makes way as Ferris, who has shaken off a leg injury, links up with Willie Faloon and Pedrie Wannenburg in the starting back row.
Andrew Trimble has recovered from a back complaint to retain his place on the right wing, while youngster Nevin Spence, who has scored two tries in his last three games, continues his centre partnership with Paddy Wallace.
Speaking ahead of the game, the province's head coach Brian McLaughlin said: "There's no doubt that Biarritz are a very good rugby team. We've already played them, we know exactly how they can play.
"We matched them well over there (in October) for 40 minutes and it's a matter of us getting out at Ravenhill on Saturday, doing the same again but extending it for 80 and making sure we get the result we want.
"They've a very good set piece side, their lineout is exceptionally strong, as we discovered, their scrum as well.
"They've a very strong maul which they've used to devastating effect in the French Championship, so those are things we've been emphasising all week.
"You've got to take care of their key decision maker (Dimitri) Yachvili who is always probing, always very much alive."
He added: "I think the fact that we've already played them means we've seen what they can do - if they are allowed quick ball and lots of possession, they can rip you apart.
"We need to make sure that if we have the ball we use it sensibly and make sure we don't give them any cheap points through ill-discipline, because if Yachvili gets a penalty anywhere in your own half he'll put you under ferocious pressure. He'll just just keep kicking the points through the posts.
"We're well aware of them, know exactly what they're capable of and it's a matter for us to match and make sure we beat them in all those areas."
With qualification for the quarter-final stages of the Heineken Cup competition still very much in Ulster's hands, Saturday's match against Biarritz represents one of the most important games in the province's history.
A win would ensure that McLaughlin's men are still very much in contention, ahead of their round 6 trip to Aironi Rugby next weekend.
Saturday's match is not yet sold out and tickets are still available. Ulster Rugby would advise supporters coming to the game (gates open 2pm) to avoid parking in the immediate vicinity of the Ravenhill grounds where restrictions may be in place, and instead make use of the Park 'n' Ride facilities at Pirrie Park and along Montgomery Road.
For supporters interested in using public transport from the city centre, there is also a Translink Metro service running from Chichester Street to Forestside along the Cregagh Road, which stops at Onslow Parade.
From there, it is just a short walk to the ground. Journey time is approximately 10 to 12 minutes. For more details, please visit www.translink.co.uk.
ULSTER (v Biarritz Olympique): Adam D'Arcy; Andrew Trimble, Nevin Spence, Paddy Wallace, Simon Danielli; Ian Humphreys, Ruan Pienaar; Tom Court, Rory Best (capt), BJ Botha, Johann Muller, Dan Tuohy, Stephen Ferris, Willie Faloon, Pedrie Wannenburg.
Replacements: Nigel Brady, Bryan Young, Declan Fitzpatrick, Tim Barker, Chris Henry, Paul Marshall, Ian Whitten, David McIlwaine.