Robertson isn't sure how the Bay fans will react to his return as "an enemy", nor that any of them will probably be backing the O-League qualifiers.
"I'm hoping I won't be getting too many taunts from the crowd and they'll respect my decision to go to Wellington," he says.
The 30-year-old, who arrived here from Canterbury United, is player/coach of the Bluewater Napier City Rovers in winter's Central League competition.
He says he left for the capital city for the opportunity to fulfil a long-term desire to play in the premiership grand final with the Matt Calcott-coached franchise team, as well as the drawcard of footing it in the O-League at the end of the year.
"It's something I've wanted to do for years," Robertson says as the Wellingtonians arrive here with a 2-1 win over Wellington Phoenix at Dave Farrington Park, Miramar, last weekend.
Earning the respect of his teammates, including former Bay United midfielder Cole Peverley who is his co-captain, and the coaching staff, is imperative.
While he has heard of the Bay players, Robertson doesn't know what they'll bring to the park after the hosts' 3-2 away loss to Auckland City last Sunday under Angell's philosophy.
On the flip side, Bay United "homeboy" Mario Alberto Barcia has traded places as a player who plied his trade with Island Bay United in Wellington last winter.
After some training and a game later, he's beginning to carve a niche or two in the lounge, so to speak, but more light is needed to roam freely.
The Argentine, who stokes the fire in the engine room, says communication among the predominantly young brigade is essential to their season.
"Kiwi boys just run around, they don't talk," says the holding midfielder who hails from the northern capital of Santiago del Estero province.
"Talk is good sometimes but in Argentina we talk too much," the 25-year-old says with a grin.
In his first year abroad and New Zealand, he is comfortable with the pace of play but is coming to terms with the physicality.
He claims not to know Robertson but Blues fans will remember how Robertson took his time to get off the ground after a Barcia tackle in Island Bay's 4-1 loss to Rovers in the Chatham Cup quarterfinals.
Barcia is used to training every day in Argentina where he started his career at Newells Old Boys, the club where Lionel Messi began his career.
The Bay signing also played for Independiente De Avellaneda as well as Aurora in Bolivia.
Having missed at least five scoring chances last weekend, shooting practice was on the Bay's agenda.
For the man who sees himself as "captain on the pitch", there's no pressure but winning is vital.
TEAMS
Hawke's Bay United: 1. Josh Hill (GK), 2. Wade Randle, 4. Ross Haviland, 5. Fin Milne, 6. Ryan Tinsley, 7. Troy Pennycooke-Morgan, 8. Alex Palezevic, 9. Sean Lovemore, 10. Victor Lekaj, 11. Mario Barcia, 12. Saul Halpin, 16. Leon Birnie, 19. Facundo Barbero, 20. Harry Morton, 21. Kosuke Mimaki, 22. Billy Scott, 24. Fane Morgan, 26. Adam McDonald (RGK).
Coach: Brett Angell
Team Wellington: 1. Michael O'Keeffe, 2. Greg Rosenthal, 3. Lee Colligan (Nico Bechar), 4. Tyler Lissette, 5. Bill Robertson, 7. Henry Fa'arodo, 8. Cole Peverley, 9. Jarrod Smith, 11. Michael Gwyther, 13. Alex Feneridis, 14. James Musa, 15. Luis Corrales, 17. Sean Morris, 19. Cory Chettleburgh, 20. Adam Cowan, 22. Dan Clarke.
Coach: Matt Calcott
