NORTH PHILADELPHIA native Gabriel Rosado walked into a boxing gym in Burbank, Calif., one day and asked one of the trainers whether he could wrap his hands. As the boxer readied to spar, he asked the same trainer whether he would work with him in the corner.

Rosado took to Jesse Reid's advice. Soon after, a new boxer-trainer relationship was formed.

"We just clicked from there," Rosado, 28, said recently, "and I just feel that I'm a much better fighter right now, and I'm learning a lot of new things."

With Reid in his corner, Rosado (21-8, 13 knockouts) will put what he's learned to the test tomorrow night at the Barclays Center in Brooklyn. He fights NABF middleweight champ David Lemieux (32-2, 30 KOs) in the headliner of an HBO "Boxing After Dark" tripleheader that begins at 10 p.m.

Rosado, who grew up in Philadelphia but now holds his training camps in Los Angeles, is coming off an August knockout of Bryan Vera as part of the new Big Knockout Boxing. That was his first fight since he started working with Reid, who has trained numerous world champions.

Before that, in January at the D.C. Armory, Rosado lost to Jermell Charlo by unanimous decision. He fought three times last year, each time with a title on the line. He lost to Gennady Golovkin and Peter Quillin by technical knockouts. His split-decision loss to J'Leon Love was ruled a no-contest after Love tested positive for a banned substance.

Lemieux, a 25-year-old from Montreal, is coming off a May knockout of Fernando Guerrero that gave him the vacant NABF title. This is his United States debut; each of his previous fights has taken place north of the border.

"I'm not taking David Lemieux lightly," said Rosado, who, before teaming with Reid, was trained by Billy Briscoe for about 10 years. "I think [Lemieux] comes in there and he tries to go for the kill; he tries to go for the knockout, throwing a lot of big shots.

"It's nothing that I haven't seen in the past. I think I've fought the best middleweights out there right now. I think I just need to use my experience and my ring smarts in this fight and we have a strong game plan in what we're going to do, and I feel that my game plan is going to succeed."

On the undercard, fellow Philly fighter Hank Lundy (25-3-1, 12 KOs) meets NABF light welterweight titleholder Thomas Dulorme (21-1, 14 KOs). For Lundy, 30, the bout signifies his HBO debut.