P.J. Carlesimo stood in the hallway outside the visiting locker room inside the Rose Garden shortly after his Nets had obliterated the Trail Blazers Wednesday night, exchanging pleasantries with several former staff and media members as they walked by.

It was in that building — one that opened with Carlesimo roaming the sidelines and shouting instructions as Portland’s head coach — that Carlesimo last led a team into the playoffs as a head coach, in the 1996-97 season.

Over the intervening 16 years, Carlesimo has had a pair of head-coaching jobs — first in Golden State for two-plus seasons, then Seattle/Oklahoma City for another year-plus — along with five years, and three championships, as an assistant with the Spurs, in addition to a year as an assistant with the Raptors before coming to the Nets prior to last season.

But now, Carlesimo is just a few weeks away from taking a team into the playoffs as a head coach, after taking over on an interim basis for Avery Johnson in late December.

The Nets head into Denver Friday night comfortably entrenched as the fourth seed in the Eastern Conference after going 4-1 to begin the Circus Trip and picking up wins in eight of their last 11 games. Carlesimo couldn’t help but admit there’s a huge difference between being the head coach of a playoff team and an assistant, which he was in San Antonio for three championships under future Hall of Famer Gregg Popovich.

“It’s night and day,” Carlesimo told The Post, “and it’s nice to have a team that’s as talented as this. You look a lot smarter when you have players like this.”