Jared Sullinger just graduated Kevin Garnett 101. Under the tutelage of his veteran mentor, the Celtics rookie has thrived on the court. Now it’s time for a new lesson: The Art of the Metaphor.

Over the years, we’ve been treated to KG’s lectures on everything from zoology to culinary arts to technology, so there’s no telling how he’ll grade this attempt at an historical metaphor from Sullinger.

“It’s a lot of hard work,” Sullinger said after recording the second double-double of his career (12 points, 16 rebounds) in an 87-79 win over the Suns, “but the train doesn’t stop here. We’ve got to keep going. We’ve got to make it to the next stop, after that the next stop, after that the next stop, so we’re the Underground Railroads.”

Ok, then. Moving on. The Celtics have won four straight, and Sullinger has averaged 9.3 points and 10.0 rebounds in that stretch. The C’s late first-round pick raised his nightly production to 5.6 rebounds, which ranks only behind top-10 selections Anthony Davis, Andre Drummond and Michael Kidd-Gilchrist among NBA rookies.

“I could care less,” said Sullinger, whose name has also been thrown around in various trade scenarios for DeMarcus Cousins. “We’re winning. We’ve won four in a row, so that’s my main focus. Last June is behind me.”

Consider Sullinger plays just 19 minutes a game, his numbers become all the more impressive. On Wednesday, however, he played a season-high 34 minutes, and his 16 boards marked a new season-high for the C’s.

“We’ve got a lot of confidence in him, and I think he’s feeling his own confidence,” said Garnett. “He’s playing like a madman. I knew he had like 10 [rebounds] or something. I didn’t know he had 16. That’s what’s up.

“He has the perfect body for rebounding. He can bump a little bit, and he has great anticipation when it comes to the ball. He can take the pounding, and he has great hands. Put all that in a pot, and you got Jared Sullinger. That’s what makes him one of the up-and-coming great rebounders in our game.”

Wait, did my ears deceive me or did we just hear another KG cooking analogy? Meanwhile, Celtics coach Doc Rivers didn’t mix metaphors when it came to Sullinger’s prowess on the glass.

“Most of the great rebounders aren’t that tall, when you think about it,” said Rivers. “They’re big, they’re physical, and they have great instincts. I think that’s the No. 1 thing. … Just think about the list of great rebounders. They just have a knack for the ball. And they have great hands, every single one of them.”

Sullinger offered a simpler explanation for his 10.6 rebounds per 36 minutes pace.

“You’ve got to have a go-get-it attitude when it comes to rebounding, and that’s what I have,” said the 6-foot-9, 260-pound rookie. “I’m just a go-getter when it comes to rebounding.”

You could almost hear Sullinger whistling “This Train Is Bound For Glory” on his way out the locker room.