Under the advice of his coaching and medical team, Manson is taking time to recover from the hectic few months on the international rowing circuit.
While bitterly disappointed, event organisers are equally excited to open the door for world champion double scullers Harris and John Storey to take on this year's 5km battle.
The big question is will their rocketing campaigns be enough to fend off the master strokes of Drysdale.
"Obviously we are very bitterly and so is Robbie, but his health and well being must come first," Wanganui Rowing Association spokeswoman and district councillor Philippa Baker-Hogan said.
For Harris it is a homecoming and to celebrate he will wear his distinctive yellow and red Aramoho Wanganui Rowing Club colours rather than his New Zealand singlet.
"I've had a decent break to allow my body to recharge. It takes a wee bit longer each year, but I've been back in training for two weeks now," Harris said.
Asked how his single scull form was, Harris said 'not too bad'.
"John is pretty good in the single and I'm not too bad. We'll give Mahe a good run for his money, although I haven't seen him lately so I don't know how his fitness is. I'm looking forward to the Billy Webb and it will be my first time on the Whanganui River in a couple of years."
In the meantime, Harris and Kerri Gowler, fresh from her win in the women's pairs with Grace Prendergast at the World Championships in Florida, will return home this Friday to attend the Wanganui Sports Awards as individual nominees.
Billy Webb organiser Kat Wade said it was truly shaping up to be anyone's race and the serious contender's bill doesn't stop there.
Twenty-two- year-old Jordon Parry has had international success this year winning gold with his teammates at the World Under-23 Rowing Championships in Plovdiv, Bulgaria. Jack O'Leary also had a stellar showing in Poldiv, taking silver with the men's quad.
"It's not every day emerging stars have the opportunity to shine against racing's elite, which makes the Billy Webb uniquely special on the NZ rowing calendar," Wade said.
Representing Rowing NZ's high performance women - Brooke Donoghue is returning to Whanganui - having narrowly missed out on taking out last year's Women's Elite grade to Lucy Spoors, Brooke has every chance to take the title this year.
"Entries for the race are coming in from Rowing Performance Centres and clubs across the country - with no clear favourite it's set to be a riveting challenge.
"Viewing of the race will be available to stream online or if you're lucky enough to be in Whanganui head down to Settlers Wharf on Taupo Quay to view all of the live action on the water and super screen," Wade said.