Harlequins director of rugby Dean Richards has warned Bristol his side are determined to have a say in the make-up of the Guinness Premiership play-offs.

Quins have rocketed up the table after winning four of their last five matches and they could yet claim a coveted spot in the top four if they maintain that form.

They host second-placed Bristol tomorrow and Richards is eager for the London club to begin claiming some major scalps.

He said: "Last weekend's victory over Northampton was our first against them for 10 years and it was a key one with such a tough period ahead of us.

"We have all of the top five to play in the coming weeks and we are under no illusions about the task ahead.

"That said, we go into the period full of confidence and there's no reason why we can't make life very difficult for the title chasers.

"We have a big say on the destination of the trophy, while finishing as high as we possibly can."

Quins winger David Strettle has been called up by England for tomorrow's RBS 6 Nations clash with Ireland so Simon Keogh fills with the number 14 jersey and Hal Luscombe replaces injured centre Stuart Abbott.

Bristol have been hit hard by injury following their comeback 22-21 triumph over Newcastle, including a hamstring problem for Alfie To'oala.

The absentees have forced head coach Richard Hill to adopt a more cerebral approach against Quins.

He said: "When you face a good defence like Harlequins', you can't subtly get around them.

"You have to use a bit of brute force and that is something we are going to lack. We are going to have to craft a few openings as opposed to battering a few."

Leicester head coach Pat Howard has selected Paul Burke at fly-half for the east midlands derby against Northampton in the hope it will spur on the Irishman's rivals for the number 10 jersey.

"Paul gets the nod at 10 this week as a reward for his performance in the win over Newcastle and also because I want to keep competition high for the position," said Howard.

"Andy Goode is recovering from his hamstring injury and Ian Humphreys had a great couple of games in Europe but I want to keep the competition strong there."

Gloucester head coach Dean Ryan is delighted by the return of James Simpson-Daniel and Ryan Lamb from injury for tomorrow's clash with bottom club Worcester.

"There are obviously injuries at the moment so to have two players like James and Ryan available for a game of this intensity and importance is great for us," he said.

"Both are excellent players and provide a real attacking threat and that will be crucial to us."

Bath face Saracens tomorrow with coach Steve Meehan desperate to banish memories of the 55-23 defeat at Vicarage Road in October.

"There is no way that you can forget that performance against Saracens," he said.

"It was a day when absolutely nothing went right for us, and everything seemed to fall into place for them.

Since then, they have strung some pretty good form together - they are up in the top half of the table, they are pushing on and this match will be very difficult for us."