Northampton and Saracens clash at Franklin's Gardens on Saturday knowing someone's perfect record in this year's LV= Cup will have to go.
The two Aviva Premiership sides have so far won three from three in the Anglo-Welsh competition, meaning they are already certain of qualifying for the knockout stages. However, the winner this weekend will know they are almost certain of a home semi-final.
International call-ups are a big issue for both teams, with Saints without 13 of their first-team squad.
The hosts have recalled Jamie Elliott, George Pisi, Samu Manoa and Ben Nutley into the starting XI, with Will Hooley - who has been on dual registration with Moseley this season - making his first team debut at fly half.
Sarries themselves have made alterations from last week's 41-8 victory over Newcastle, including handing starting berths to Marcelo Bosch and Michael Tagicakibau. Petrus du Plessis starts at tighthead prop and Justin Melck packs down at number eight.
There are two other all-English ties on Saturday, including Exeter travelling to Worcester. The Chiefs could still win Pool 2 if Friday's results for Sale and Leicester go in their favour.
Exeter are virtually at full strength as they look to make it a hat-trick of cup wins, though Jack Nowell is an obvious absentee as he makes his debut for England against France on the same day.
The Warriors, meanwhile, see plenty of changes from the team that faced the Sharks last time out, including handing David Lemi his first appearance since November.
Director of rugby Dean Ryan also gives Chris Pennell his first start in almost a month, while Josh Drauniniu, Ignacio Mieres and Jeremy Su'a all return to the backline.
Gloucester and Wasps meet at Kingsholm with nothing but pride to play for; the Cherry and Whites are able to welcome back Henry Trinder from injury, with the centre forming a strong-looking midfield partnership with Mike Tindall.
Rob Cook and Shane Monahan return to the starting line up in the backs, while there is a new-look back row in Sione Kalamafoni, Matt Cox and Gareth Evans.
Their opponents from the capital have totally changed their front row - Ricky Reeves, Carlo Festuccia and Phil Swainston all get the chance to start. In fact, only James Cannon and Rory Pitman retain their places in the pack that started against London Irish.
Scrum-half Brett Sheehan is in line for his first appearance in black and gold after recently joining Wasps, who have also retained the services of Kevin Davies, on loan from London Welsh.
The other fixture sees London Irish host Scarlets, with the main point of interest being the return from injury of Wales international centre Jonathan Davies.
He is part of a visiting line-up that also includes another long-term injury victim in Deacon Manu, the prop having not appeared since fracturing arm in RaboDirect PRO12 action last September.
The Exiles have recalled James O'Connor, Ofisa Treviranus, David Paice and CJ Van Der Linde as they bid to record their first cup triumph of the campaign. Tomas O'Leary and Shane Geraghty will continue at half back with Eamonn Sheridan and Fergus Mulchrone together in the centres.