Patriots tight end Rob Gronkowski steamrolled the Redskins in December, catching six passes for 160 yards and two touchdowns. (John McDonnell/THE WASHINGTON POST)

The way Bill Belichick describes Rob Gronkowski, his chiseled-from-granite tight end on the New England Patriots, could seem trite. “He’s always got a smile on his face, and he’s always working hard,” Belichick said Thursday, two days before the Patriots host the Denver Broncos in an AFC divisional playoff game.

But go back six years or so, when Gronkowski was a two-way player for Williamsville North High, outside Buffalo. The opponent was nearby Clarence, and Gronkowski lined up at defensive end on the right side. Clarence pitched the ball to a running back, who ran the opposite way. And there was Gronkowski, barreling in on the ballcarrier.

“I wanted to drill him,” Gronkowski said Thursday.

As he closed in for the tackle, through his face mask, came an ear-to-ear smile.

“It was almost like he was giggling,” said Mike Mammoliti, Williamsville North’s coach. “His eyes were big as saucers. He caught this kid maybe two or three yards from the sideline, and he blew him up, sent him all the way into our bench. And you just had this sense that he just enjoyed what he did.”

Gronkowski’s enjoyment of football, combined with ridiculous physical skills and a 6-foot-6, 265-pound frame, have him entering his second playoff game at age 22 with historic accomplishments.

Only five other tight ends have ever had 90 catches in a season, Gronkowski’s total this year. None has finished with more than Gronkowski’s 1,327 yards, which set a record in 2011. The old standard for touchdown catches by a tight end in a single year was 13, set by San Diego’s Antonio Gates in 2004 and matched by San Francisco’s Vernon Davis in 2009. Gronkowski equaled that total in the 12th game of the season, and finished with a record of 17.

And he’s done it all in a way that has endeared him to a Patriots fan base that badly wants another Super Bowl championship. “Gronk,” as he is known in these parts, has goofily embraced his new celebrity, surprising even some who know him well.

“There were kind of question marks with Robby, because he’s kind of a shy kid. He sometimes seems like he doesn’t like to talk,” said Dana Dimel, Gronkowski’s position coach at the University of Arizona. “If you’re an NFL team and you’re interviewing him, he could seem like maybe he’s a distant kind of guy. But he’s not. He loves football.”

That he comes by naturally. His father Gordy played on the offensive line at Syracuse, and his older brother Dan — the second of five Gronkowski boys — played tight end at Maryland and is now with the Cleveland Browns. Older brother Chris initially went to Maryland, then transferred to Arizona and is now a fullback with the Indianapolis Colts. Youngest boy Glenn will play next year at Kansas State.

Gordy Gronkowski owned an exercise equipment dealership — G&G Fitness — and the boys weren’t even in high school when they started lifting weights. That had a direct impact on Gronkowski’s college career, which he began by catching 28 passes, including six touchdowns, as a true freshman for the Wildcats.

“That time after you sign guys, from January to July, most players don’t understand how to train,” Dimel said. “But the Gronkowskis, their dad had a good understanding of what to do, and he really got them ready. Rob was able to hit the ground running.”

But after catching 75 passes and 16 touchdowns in his first two seasons, Gronkowski ran into a problem with his back. He had surgery, and missed all of 2009 — which was supposed to be his breakout year.

“It was miserable,” Gronkowski said. “It wasn’t cool seeing your boys every single day out on the field together, having fun and everything. You’re just sitting there just doing nothing, just basically sitting on the couch, not having a good time.”

Yet when it came time to determine his future, Gronkowski weighed his options, and entered the 2010 NFL draft — even though he hadn’t played a snap in a year and a half, even though, had he stayed, “he could have been a top-10 pick,” Dimel said. The Patriots got him in the second round, trading up two spots and giving Oakland a sixth-round pick to snag him with the 42nd choice. They were optimistic, but with a year off, who knew?

“The reality is, you really don’t know what’s going to happen that next year,” said Nick Caserio, New England’s director of player personnel.

What happened: 42 catches and 10 touchdowns as a rookie, then the record-setting explosion this season. Some of that success can be traced to Gronkowski’s stature and skills. After he caught six passes for 160 yards and two touchdowns against Washington in December, Redskins defensive coordinator Jim Haslett said: “I heard someone on TV say, ‘Well, he’s got nine inches on [his defender]. I said, ‘Well, put anybody else on him and he’s got six.’ ”

But Gronkowski, the Patriots say, also works at his craft. He is only 22, only in his second year in the league. But his errors are down, and his responsibilities are up.

“Once he sees it, once he understands it, you usually don’t have to worry about it really ever again,” Belichick said. “That’s really the mark of a good player, being able to take an experience, learn from it, and then be able to apply it the next time it comes up.”

He has grown and developed, quite quickly, into an all-pro, smiling all the way.