Gloucester are one point behind Irish in Pool One, but victory at the Madejski Stadium this weekend and then in next Saturday's Kingsholm return fixture would see them control the group.
They have already beaten Irish away from home in the Aviva Premiership this season, but rugby director Nigel Davies has not taken too much notice of that result during preparations.
"That was only the second week of the season and we were all just finding our feet, so I don't think you can read too much into that game," Davies said.
"It will be interesting to see how they (Irish) approach this game. Obviously they've got a lot to do in the Premiership, and we still have big ambitions in the league ourselves.
"We are going to go pretty full on, as we do for every competition. We will change things up a little bit and give opportunities, but it's a strong team."
England back Freddie Burns switches from fly-half to centre, with Tim Taylor wearing the number 10 shirt, while there are also starts for wing Shane Monahan and scrum-half Dan Robson, with a powerful bench including Mike Tindall and Ben Morgan.
David Paice and Jonathan Joseph return to the London Irish side.
Sailosi Tagicakibau moves from outside centre to inside centre with Joseph taking the 13 shirt. Matt Garvey moves to the second row with Gibson coming into the back row and Halani Aulika starts at tighthead prop.
London Irish director of rugby Brian Smith told the club's official website: "Both sides are well placed in the group and the next two week's will go a long way to seeing which side goes through to the knock out stages. Gloucester are enjoying a good run this season and will be a difficult opposition tomorrow, so we will need to be at our best to get the result."
London Irish team: 15. Tom Homer; 14. Topsy Ojo; 13. Jonathan Joseph; 12. Sailosi Tagicakibau; 11. Anthony Watson; 10. Ian Humphreys; 9. Darren Allinson; 1. Max Lahiff; 2. David Paice; 3. Halani Aulika; 4. Bryn Evans; 5. Matt Garvey; 6. Declan Danaher (Captain); 7.Jamie Gibson; 8. Ofisa Treviranus
Replacements: 16. Scott Lawson; 17.Jerry Yanuyanutawa; 18.Leo Halavatau; 19. Kieran Low; 20. Chris Hala'ufia; 21. Guy Armitage; 22. Shane Geraghty; 23. Jack Moates
Gloucester team: Martyn Thomas; Charlie Sharples, Tim Molenaar, Freddie Burns, Shane Monahan; Tim Taylor, Dan Robson; Nick Wood, Huia Edmonds, Shaun Knight; Tom Savage, Jim Hamilton (capt); Sione Kalamafoni, Matt Cox, Gareth Evans
Replacements: Darren Dawidiuk, Dan Murphy, Rupert Harden, Will James, Ben Morgan, Dave Lewis, Mike Tindall, Rob Cook.
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