South Africa international Ruan Pienaar has returned to the Ulster rugby squad ahead of their Heineken Cup opener against Castres Olympique at Ravenhill on Friday.

Pienaar returns to the squad after an impressive stint with the Springboks during the Rugby Championship.

New Ulster head coach Mark Anscombe could opt to pair the versatile 28-year-old with either scrum-half Paul Marshall or out-half Paddy Jackson this weekend.

Provisional Ulster squad:

Forwards: Rob Herring, Rory Best, Nigel Brady, Neil McComb, John Afoa, Tom Court, Adam Macklin, Callum Black, Johann Muller, Dan Tuohy, Lewis Stevenson, Stephen Ferris, Mike McComish, Iain Henderson, Chris Henry, Nick Williams.

Backs: Ruan Pienaar, Paul Marshall, Michael Heaney, Paddy Jackson, Paddy Wallace, Darren Cave, Luke Marshall, Andrew Trimble, Tommy Bowe, Craig Gilroy, Jared Payne.

Elsewhere, lock Neil McComb and hooker Nigel Brady also return to the panel while Nick Williams is also included despite suffering a rib injury late in the province’s 25-0 victory over Connacht on Friday.

Ulster say the big number eight is responding well to treatment and a decision on his involvement will be made later in the week.

Prop Declan Fitzpatrick aggravated a medial ligament injury prior to last week’s match and remains unavailable, while Australian-born flanker Sean Doyle is ruled out for six weeks after suffering a broken leg playing Ulster Bank League rugby for Dungannon at the weekend.

Ulster were Heineken Cup finalists last year, and are unbeaten so far this season in the RaboDirect Pro12.