The other forced change is the shock departure of Thornbury's mate Steve Crosbie, as the talented first-five flew home yesterday to take up a professional contract with Munster Rugby, who are four rounds into the Guinness Pro12 season.
"Didn't know anything about it until Tuesday morning, 6.30am phone call. Bloody great surprise to me," Caskey said.
"Didn't want to stand in his way. A bit unfortunate with the timing of it. Another month would've been nice."
However, the decision to use Dane Whale as starting second-five against Poverty Bay is looking even wiser in hindsight, as he will now slot comfortably back into the No10 jumper while Te Tua Kemp will play the curtain raiser and then sit on the Heartland bench as backup.
Despite these forced changes while injuries will still keep centre Craig Clare away for another week, Caskey still has the confidence to persist with squad rotations in the positions where there is still plenty of depth.
The chance for Roman Tutauha to captain the Whanganui Maori means Cole Baldwin is first-string hooker, while young wider squad member Jack Yarrall is set to make his senior representative debut.
"I've been wanting to give Cole another start and I told Jack all along, I wanted to give him a chance this season.
"He's trained with us all year, I think he deserves an opportunity."
Having debuted himself last weekend, prop Gabriel Hakaria remains bracketed on the bench as enforcer Tietie Tuimauga trained well on Tuesday night and could be back a week earlier than expected.
Caskey was bringing in staff to test the prop at training yesterday , but will take a "no risk" approach with finals rugby on the horizon.
"If he gets through tonight alright, he'll come in."
Also back in better spirits is winger Samu Kubunavanua, after the x-ray on his ankle came back all clear, and he rejoins the squad on the bench with good timing after Cameron Crowley was lost for the season.
Kane Tamou, who hasn't put a foot wrong on his rare chances, will rotate again with No1 halfback Lindsay Horrocks.
In total, there are nine survivors from the Wanganui team who dispatched Thames Valley 47-27 in Paeroa last year, and ironically there are the same number in the visiting team.
The squad is reinforced by Waikato loan players Rupeni Vakacegu (flanker), Norman Solofa (No8) and Jonnie Te Ruki-Chambers (Waikato).
Their all-2015 NZ Heartland representative back three in wingers Tyrone Keith and Lance Easton, along with fullback Moss Doran, are to be respected - the latter two players being standouts at Cooks Gardens last November against the Australian Barbarians.
While the winless Thames Valley were competitive in their opening games with Horowhenua-Kapiti (34-30), North Otago (30-22), King Country (22-22) and Wairarapa Bush (28-18), the wheels fell off in the 62-16 hammering at home against South Canterbury last weekend.
Kick off is 2.30pm.
The teams are
Wanganui
1. Hamish Mellow; 2. Cole Baldwin; 3. Viki Tofa; 4. Peter Rowe (c); 5. Gavin Thornbury; 6. Tremaine Gilbert; 7. Jamie Hughes; 8. Malakai Volau; 9. Kane Tamou; 10. Dane Whale; 11. Michael Nabuliwaqe; 12. Kameli Kuruyabaki; 13. Blake Hohaia; 14. Te Rangatira Waitokia; 15. Ace Malo.
Reserves - Forwards: 16. Jack Yarrall; 17. Tietie Tuimauga/Gabriel Hakaria; 18. Bryn Hudson; 19. Ranato Tikoilosomone. Backs: 20. Lindsay Horrocks; 21. Te Tua Kemp; 22. Samu Kubunavanua.
Thames Valley
1. Romy Chies; 2. Hayden Wisnewski; 3. Haerengarangi Renata; 4. Kent McFarlane; 5. Matt Rolston; 6. Rupeni Vakacegu; 7. Connor McVerry. 8. Norman Solofa; 9. Dene Beau; 10. Chris Doak; 11. Tyrone Keith; 12. Jonnie Te Ruki-Chambers; 13. Jone Koronisagna; 14. Lance Easton; 15. Moss Doran.
Reserves - Forwards: 16. Rowan Dare; 17. Nic Judd; 18. Josh Elgroan; 19. Tim Erceg. Backs: 20. Ben Bonnar; 21. Jack Metters; 22. Joape Naluwavu.