Harlequins coach John Kingston believes his side face 'the sternest test in Europe' when they take on Leicester in the Powergen Cup quarter-finals this weekend.

Leicester might have lost an 11-match unbeaten European record to Llanelli six days ago, but they will arrive at The Stoop tomorrow as firm domestic cup favourites.

Tigers can also summon added motivation from their cup demise last season - a 22-18 semi-final defeat against Quins.

It proved to be the one prize that got away during a campaign when European, Premiership and Premiership play-off silverware all ended up in Leicester's bulging trophy cabinet.

Quins' quarter-final mission, even on home soil in front of an anticipated capacity 9,000 crowd, appears incredibly tough.

But take out injured international trio Keith Wood, Dan Luger and David Wilson - then consider a miserable run of five successive Premiership defeats, including a 38-21 home reversal against Leicester three days before Christmas - and Tigers can rightly lick their lips in anticipation.

"We are facing one of the sternest tests available in northern hemisphere rugby," admitted Kingston.

"Leicester are a formidable outfit in normal circumstances, but to have to face them in the Powergen Cup off the back of their defeat against Llanelli, will make them even more determined to get a result at The Stoop.

"Having said that, we are looking forward to the challenge, and we hope to be able to compete with what is currently the best team in Europe."

Leicester have spent the week taking out their frustration in training, hurt to a man by an unexpected 24-12 Stradey Park collapse, a defeat which would have cost them home Heineken Cup quarter-final advantage had Leinster not come unstuck even more spectacularly against Toulouse.

Tigers boss Dean Richards anticipates making few changes as his team target an immediate response after the Scarlets left them feeling distinctly off colour.

England star Austin Healey is still suspended, while flankers Lewis Moody (hip) and Will Johnson (sprained ankle) are both struggling, so Martin Corry could switch to blindside flanker with Adam Balding or Peter Short selected at number eight.

Former Springboks lock Johan Ackermann is on course to make his Northampton debut in Saturday's quarter-final encounter at Saracens.

The 31-year-old linked up with Saints last week, and is set for a bench role, given Olivier Brouzet's pending return from a shoulder problem alongside second-row partner Jon Phillips.

Northampton coach Wayne Smith has named a 29-man squad, and could again pin his faith in scrum-half rookie James Brooks.

Brooks, normally a fly-half, wore the number nine jersey with distinction opposite Wales and Lions ace Rob Howley when Saints beat Heineken Cup opponents Cardiff last Saturday, suggesting he could earn another opportunity while Matt Dawson remains sidelined through injury.

Dom Malone, Northampton's established deputy when Dawson is absent, faces a fitness test tomorrow on his troublesome hamstring.

Saints will hope history repeats itself, having beaten Saracens in a quarter-final thriller two years ago and subsequently going all the way to Twickenham.

Saracens make five changes following their last-minute Shield success against Bordeaux-Begles, calling up wing Tom Shanklin, fly-half Jannie De Beer, prop Pierre Durant, lock Kieran Roche and flanker Kris Chesney, who returns after a long-term injury.

Premiership basement club Leeds welcome back three key players for Sunday's Headingley appointment with cup holders Newcastle.

South African Braam van Straaten, who was unavailable during the recent Parker Pen European Shield group rounds, scrum-half Scott Benton and lock Tom Palmer all return to give Leeds a considerable triple boost.

"Our European Shield campaign has given us some momentum, and this game provides an opportunity to put down a marker," said Tykes coach Phil Davies.

Newcastle, destroyed 53-17 by Newport in a Heineken Cup clash last Friday, rested several players for that game, but England fly-half Jonny Wilkinson should spearhead the returning masses.

Player unavailability has hit both London Irish and Gloucester ahead of their Madejski Stadium meeting on Sunday.

Kieron Dawson (knee), Richard Bates (shoulder), Darren Edwards (elbow), Jeff Fahrenson (back), Eddie Halvey (knee) and Neal Hatley (arm) are all Exiles' casualties, with Dawson's absence prompting a back-row reshuffle as James Cockle starts and England squad member Declan Danaher switches from blindside flanker to openside.

Gloucester's worries are mainly in the front row, where Trevor Woodman and Olivier Azam are both suspended, and Phil Vickery is injured.

Long-serving prop Andy Deacon takes over captaincy duties from Vickery.