MACAU — Chris Algieri likes to visualize things before they happen.

So it was odd that the fighter from Huntington, L.I., said he hadn’t considered what the day after his welterweight title fight with Manny Pacquiao would look like.

“I really haven’t,” Algieri said of Saturday’s match on HBO pay-per-view at the Venetian Resort Casino in this fast expanding city.

But someone else had:

“My business manager Kevin Rooney has been thinking about that stuff,” Algieri went on. “I’m sure he’s got a whole master plan that we’ll talk about at the victory party by the pool.”

Kevin Rooney?

Was he referring to the balding guy who once trained Mike Tyson, guiding him to a heavyweight championship in 1986?

No, he was talking about his son, Kevin Rooney Jr., who has toiled in boxing’s shadows, first as a publicist, then as a middling junior middleweight before emerging as Algieri’s business manager.

“He had jumped around the boxing business a little bit and when this opportunity came up — I needed help,” Algieri says. “And I really couldn’t think of anyone better.”

During the tense negotiations for the Pacquiao fight, Algieri leaned on Rooney Jr. for advice since he didn’t have a manager.

The two had a history together, dating back to the early days of Star Boxing, when Rooney Jr. was a publicist for promoter Joe DeGuardia and Algieri was an unknown up-and-comer.

Rooney Jr. was also fighting and the two would travel to each other’s bout, giving each other tips. When the fight was secured in July, Algieri needed someone to help handle the day-to-day tasks of running Chris Algieri Boxing, Inc., a corporation he formed to maximize exposure.

So he asked Rooney Jr. to meet him for lunch.

“I couldn’t even handle my schedule,” says Algieri. “I was double- and triple-booking things.”

Rooney Jr., whose first day on the job was on Sept. 1, operates as a jack-of-all-trades for Algieri, sorting through media requests, hiring sparring partners and combing through potential business opportunities.

Now, he hopes to expand his business portfolio to include other fighters to manage.

“I’ve said all along when I was a kid and even growing up with my father that I always wanted to be in the boxing industry,” Rooney Jr. said on Monday following a workout with Algieri and his trainers, Tim Lane and Keith Trimble. “And I saw myself more on the management side because it’s more of a personal relationship with the fighter. Chris keeps saying I’m his right-hand man.”

Regardless of what happens on Saturday, it will likely lead to a number of business opportunities for Algieri, who has a Master’s degree in clinical nutrition.

But it could also signal the arrival of Rooney, who sees parallels in his work with Algieri (20-0, eight knockouts) and what his father accomplished with Tyson.

His father was nearly 30 when Tyson vanquished Trevor Berbick on Nov. 22, 1986 to become the youngest heavyweight champion.

Rooney Jr. will be 30 on Dec. 3, and hopes to be celebrating a birthday along with Algieri’s WBO welterweight title from Pacquiao (at a catch-weight of 144 pounds) at a victory celebration.

“It’s kind of come full circle,” said Rooney. “People always ask me if I would follow in my father’s footsteps and I think I have, just in a different way.”

Rooney Jr. has memories of attending Tyson’s training camps with his father when he was 3, and even of vacationing with the Brooklyn brawler.

In Rooney Jr., Algieri has a boxing lifer and a kindred spirit. They are both college educated — Rooney Jr. has a degree in marketing from Fordham — are around the same age (Algieri is 30); are both extremely health conscious and have the same chiseled, bearded features.

The two are inseparable.

“His mother was the first who said it, ‘You could be my son,’ ” Rooney Jr. says of Algieri’s mom. “It’s kind of steamrolled that every person we meet for the first time will ask, ‘Are you the brother?’ We do the same things, we say the same things. It’s pretty funny. We’re just having a good time with it.”