Pool A

Tomorrow

London Wasps v Newport Gwent Dragons, 3pm

If Gloucester lose by more than seven points, Wasps will advance if they win. The Dragons need a bonus-point win to have a chance of making it all Welsh semi-finals. Wasps have lost eight players to England, but still name a powerful side. The Dragons are boosted by the arrival of Hoani MacDonald, the New Zealand Maori forward.

Newcastle Falcons v Gloucester, 3pm

Gloucester have lost only Luke Narraway to England with Olly Barkley released and should win comfortably. Newcastle have all kinds of problems up front after injuries to Carl Hayman, Ross Beatie and Adam Balding in the defeat by Wasps last Friday. They have only beaten Gloucester once in their last 12 meetings.

Pool C

Tomorrow

London Irish v Ospreys, 3pm, BBC Two Wales

The pool of calculators. If Ospreys, the champions, win they are through. If Irish win by more than seven points they could go through. But even if they do, they will be out if there is a three-way tie should Worcester win, too. In that event the pool will be decided by results between those three sides. If it is a ten-point tie, Ospreys are through with the most match points (six). If it is a nine-point tie then Ospreys would need to score two tries to progress. Got it? Both sides are almost at full strength and there is no rest for Irish's two Pacific Islanders backs; Seilala Mapusua and Sailosi Tagicakibau.

Worcester Warriors v Harlequins, 3pm

Worcester must win and hope the maths goes their way. With a Heineken Cup place up for grabs, it is worth taking seriously. Harlequins are out, but both sides are close to full strength. Worcester have Rico Gear back and Pat Sanderson may make his first appearance of the season off the bench after recovering from a leg injury. Nick Evans, the All Blacks fly half, returns from injury and is on the bench for Harlequins.

Pool D

Today

Northampton v Scarlets, 2.30pm, BBC One

If the Scarlets draw or win they are through. Northampton will have one eye on events at Bristol because unless they win with a bonus point they know victory alone might not be enough. Northampton have their three Scotland players; Euan Murray, Sean Lamont and Scott Gray back from training camp.

Bristol v Saracens, 2.30pm

If Scarlets lose and Saracens win with a bonus point they will go through unless Northampton get one. Glen Jackson, Hugh Vyvyan and Michael Owen return for Saracens. The Southern hemisphere cavalry — Ben Jacobs, the Waratahs centre, Bradley Barritt, the Sharks centre and the Wikus Van Heerden, the Blue Bulls back-row and South African World Cup winner, — have arrived but are not considered. Saracens won 23-16 at Bristol a month ago in the Guinness Premiership.