Aironi v Leicester (Pool 4, Today 1.30pm)
Already without Anthony Allen and Manu Tuilagi, Leicester have lost another centre, the Argentine Horacio Agulla. Andrew Forsyth comes in to partner Matt Smith.
Montpellier v Leinster (Pool 3, Today 1.30pm)
Leinster begin the defence of their crown on French soil without Brian O'Driscoll, who is out for six months following shoulder surgery. Fergus McFadden steps in to partner Gordon D'Arcy in the centre. Having tweaked a muscle in training in midweek, prop Cian Healy is also on the injured list for the Irish province.
London Irish v Edinburgh (Pool 2, Today 1.30pm)
All Black Bryn Evans switches from the second row to the blindside flank for Irish. "I think we can go all the way," the former Hurricanes player said. Edinburgh are without their injured points machine, Chris Paterson.
Scarlets v Castres (Pool 1, Today 3pm)
Rhys Priestland, who has been out with shoulder damage since orchestrating Wales' World Cup quarter-final win against Ireland last month, returns on the bench for Scarlets. Stephen Jones starts at fly-half.
Ospreys v Biarritz (Pool 5, Today 3.40pm)
New Samoan recruit George Stowers makes his debut on the blindside flank for Ospreys. Former Wales captain Ryan Jones has to settle for a place on the bench.
Ulster v Clermont Auvergne (Pool 4, Today 3.40pm)
Morgan Parra, France's World Cup fly-half, returns to the more familiar realm of scrum-half for the highly-fancied Clermont at Ravenhill. David Skrela wears the No 10 jersey. Lee Byrne and Nathan Hines are also in the visitors' ranks.
Munster v Northampton (Pool 1, Today 6pm)
England flanker Tom Wood returns on the openside as Northampton seek to exorcise the ghost of their second-half capitulation to Leinster in last season's final. Phil Dowson drops to the bench for Jim Mallinder's Saints.
Glasgow v Bath (Pool 3, Tomorrow 12.45pm)
World Cup winning fly-half Stephen Donald will be waiting in the pitch-side wings for his Bath debut. Tom Heathcote starts in the pivotal role for a game that pits the coaching wits of Sir Ian McGeechan against Sean Lineen, inside-centre in his Grand Slam winning Scotland team in 1990.
Saracens v Treviso (Pool 5, Tomorrow 3pm)
John Smit, South Africa's 2007 World Cup-winning captain, makes the Sarries squad for the first time but will probably appear from the bench. "It is our aim to be competing with the likes of Leinster, Munster and Toulouse to be the best in Europe," Mark McCall, Saracens director of rugby, said.
Toulouse v Gloucester (Pool 6, Tomorrow 3pm)
Gloucester are without the suspended Eliota Fuimaono-Sapolu but have their other errant World Cup centre, Mike Tindall, in their starting XV. Captain Luke Narraway drops to the bench with Peter Buxton alongside Akapusi Qera and Alasdair Strokosch in the back row for the Cherry and Whites.