Kevin Garnett’s booming voice echoed across the gym. His tone sounded irritable, almost combustible.

A group of Timberwolves players were scrimmaging that morning in September 2001, an informal gathering a few days after the 9/11 terrorist attacks.

I stopped by Target Center to gauge the Wolves’ concerns about traveling to Europe in early October for preseason games. The goal was to talk to Garnett, if possible.

No dice.

Something in the scrimmage made him spitting mad. The reason remained unclear, but he screamed and boiled like a kettle of hot water. He scowled as he walked off the court toward the locker room.

That was my first glimpse of Garnett’s volcanic intensity behind closed doors. The youngsters that make up the current Wolves roster will get to experience it soon enough, a jolt that veteran guard Kevin Martin promised would turn the locker room “upside down.”

“It’s going to be a shock to the older guys [too],” coach Flip Saunders said.

Garnett’s competitive spirit has been revisited and romanticized since news broke of his homecoming. Few understand his fury as much as former teammate Wally Szczerbiak.

He heard it and felt it as a young player. And he didn’t always like it.

But Szczerbiak said he believes Garnett’s return is a positive development for an organization attempting to rebuild itself around a collection of young, impressionable talent.

“He brings complete focus and attention,” Szczerbiak said. “And he doesn’t allow other guys to waver from that. If he’s going to be putting in the time and the focus and energy at practice, he expects all of his teammates to do the same thing and he holds them to that standard.”

The Wolves orchestrated KG’s homecoming largely on the premise that he’ll foster the growth of their young core. Because this trade looks illogical if judged purely on production and managing assets.

Swapping Thad Young for Garnett does not make the Wolves a better team. More interesting, but not better, at least in the short term.

Nobody should cling to the notion of a Big Ticket Revival. That’s not happening. Da Kid is now Da (Old) Man.

This move offers the Wolves a chance to sell more tickets and excitement — at least temporarily — in an arena that resembles a graveyard many nights. More than anything, even feel-good memories, Garnett’s return provides the young Timberpups a template for how to become a successful NBA player.

They better have thick skin.

And practice hard.

And show a commitment to defense.

And put their phones away in the locker room before games or “he’ll throw them in the toilet,” Saunders said.

Garnett is notoriously demanding and relentlessly competitive. Szczerbiak witnessed it early in his career, so he understands what’s in store for this group of youngsters. “I think he has a sincere nature of wanting to see the Timberwolves succeed,” Szczerbiak said. “So he’s going to do whatever he can to rally those guys together and figure out a way to teach them how to win games and be successful in the NBA.”

Szczerbiak had a rocky relationship with Garnett at times. Their personalities clashed. They’re both headstrong. They didn’t always get along.

One of their altercations became public, but Szczerbiak says they also had other dust-ups. He laughed about it Friday and noted that it was many years ago.

“When you play for a long time with a guy, you’re going to have things here and there,” Szczerbiak said. “Overall, it made us stronger. We had a stronger relationship and more respect for each other. But there’s no question, there were some rocky times. It’s not always peaches and cream, so to speak.”

Szczerbiak said Garnett showed him more respect as he grew older and the two mended their differences over time. Szczerbiak said Garnett pushed and challenged every teammate in specific ways.

“He handled every guy different,” he said. “He handled me different than other rookies and I’m sure he’s going to handle each guy different in that locker room.”

The word “mentor” has become an overused angle in sports. In some cases, that relationship actually produces something meaningful. Sometimes, it’s hogwash.

Szczerbiak views Garnett’s return home differently. He believes Garnett’s influence on a young roster will help shape an “overall culture.”

“I think just having KG around that locker room, his work ethic, his professionalism,” Szczerbiak said, “I think that would be a huge asset.”

And if the locker room gets turned upside down in the process, that’s not the worst thing in the world.