The match will be Casey's 235th appearance for Exiles and the Irishman, who has spent more than a decade with the club, is sure to be given a rousing send-off.
Delon Armitage also starts in his final game before leaving for Toulon while the departing Paul Hodgson and Kieran Roche are amongst the replacements.
Nick Kennedy is not involved as he is injured and Matt Garvey makes way for Casey.
The match will also be the last in charge for coach Mike Catt, who is leaving to join England's coaching team.
"Tomorrow gives us the opportunity to continue the momentum we gained from the win over Worcester to take into our pre-season. It will also mark the end of an era to players who have been great servants to our club. I am sure the supporters will turn up in their numbers to say goodbye," said Exiles head coach Toby Booth.
Irish: 15. Tom Homer; 14. Delon Armitage; 13. Jonathan Joseph; 12. Joe Ansbro; 11. Sailosi Tagicakibau; 10. Steve Shingler; 9. Darren Allinson; 1. Max Lahiff; 2. David Paice; 3. Leo Halavatau; 4. Bryn Evans; 5. Bob Casey (Captain); 6. Jamie Gibson; 7. David Sisi; 8. Ofisa Treviranus.
Replacements: 16. James Buckland; 17. Paulica Ion; 18. Faan Rautenbach; 19. Matt Garvey; 20. Kieran Roche; 21. Marland Yarde; 22. Adrian Jarvis; 23. Paul Hodgson.