Penn State introduced Bill O’Brien, the New England Patriots’ offensive coordinator, as its new football coach Saturday. Along with being forever known as the successor to Joe Paterno, O’Brien takes over a program at a university that is reeling from the Jerry Sandusky child-abuse scandal and has been criticized by former players for going outside the community to find a replacement for Paterno.

In normal circumstances, replacing a coach who served almost a half-century is a daunting task. Factoring in both the scandal that rocked Penn State this season when Sandusky, a former defensive coordinator, was charged with molesting 10 boys over several years, and the dissension in a tradition-rich environment, O’Brien enters a situation that is challenging as well as unprecedented.

Those who know O’Brien best cite his Ivy League smarts, fiery temper, football acumen and deft people skills as reasons he will thrive at Penn State. They describe O’Brien, 42, as a likable and quick-witted Boston Irishman whose career has been shaped in large part by the need to find the best medical care available for his 9-year-old son, Jack, who has a severe developmental disability.

“If there’s anyone that can do it, he can do it,” said Syracuse coach Doug Marrone, who coached with O’Brien at Georgia Tech and is one of his closest friends. “He’s faced challenges and he’s handled them with excellence. He’s a tireless worker, extremely bright and a problem solver. The best way to describe him is that there’s no challenge that he couldn’t overcome.”

Still, there are plenty of questions, including O’Brien’s lack of head coaching experience, his ability to recruit after a five-year absence from the college game, and a 1-22 record as Duke’s offensive coordinator.

He will also be coaching the Patriots until their playoff run ends, which could be a significant obstacle to improving Penn State’s pedestrian recruiting class.

But those who have been around O’Brien say his intelligence, certified by a degree from Brown, Paterno’s alma mater, will help him overcome his limited experience.

“Either you’re smart or not smart,” said Joe Alleva, the Louisiana State athletic director, who held the same position at Duke when O’Brien was the offensive coordinator there in 2005 and 2006. “It’s not something you learn. He’s a smart guy. He’s been around some really good people. I think he’ll do a good job.”

O’Brien’s big break in coaching, becoming George O’Leary’s offensive coordinator at Notre Dame in 2001, initially fell through when O’Leary lost the job after five days for lying on his resume.

Instead, the turning point in his career came in 2007 when he took a large pay cut as the offensive coordinator at Duke to essentially become the NFL’s version of a graduate assistant in New England.

O’Brien performed the grunt work of breaking down film, a job typically held by coaches more than 10 years younger. He proved himself quickly, however, rising through the ranks as Eric Mangini and Josh McDaniels had done.

“It was interesting to have someone that age, again with that background, willing and wanting to take that position,” said Scott Pioli, the Kansas City Chiefs’ general manager, who served as the vice president for player personnel with the Patriots.

“That says a lot about Bill’s humility. He’s got a great balance of humility and confidence.”

A lifelong Patriots fan who often showed his Duke quarterbacks clips of Tom Brady, O’Brien soon became Brady’s coach, impressing Patriots coach Bill Belichick with his football intelligence and work ethic.

O’Brien was promoted to wide receivers coach in 2008, then became quarterbacks coach and in 2011 was named offensive coordinator. (It is believed that O’Brien also called plays in 2009 and 2010.)

With 428 yards per game, the Patriots have the league’s second best offense, trailing only the New Orleans Saints, though O’Brien may be better known for his sideline shouting match with Brady during a game at Washington in December.

O’Brien’s former players at Duke were not surprised at O’Brien’s ascension, describing him as hot-tempered but with a purpose.

“He’s a tough coach and he made me a better player,” said Thaddeus Lewis, who was a freshman quarterback at Duke in 2006 and now plays for the Cleveland Browns. “He actually taught me the right way to do things, and that was important to me.”

Another former Duke quarterback, Zack Asack, recalled being dressed down by O’Brien during his freshman year when he could not diagram some of the Blue Devils’ formations on the grease board.

“He got on me and started yelling at me that it was ridiculous that I didn’t know them,” he said. “He expected a lot out of his quarterbacks, and I came in and studied them and to this day I could write them up on the board.”

Asack said that after O’Brien left Duke, he continued to apply the coach’s lessons about the rotation of safeties and defensive backs, reading coverage while coming to the line.

“He’s a real players coach,” Asack said. “He can relate to the players.”

O’Brien had spent two years coaching at Brown before going to Georgia Tech in 1995. There, he was saddled with tasks like picking up Ralph Friedgen at the airport when Friedgen came to O’Leary’s staff as offensive coordinator. He also coached there with Maryland coach Randy Edsall, the Vanderbilt offensive coordinator John Donovan and the former Duke coach Ted Roof.

But the most important connection O’Brien made at Georgia Tech came through Marrone. He introduced O’Brien to his future wife, Colleen, who had gone to Atlanta to visit Marrone’s wife, Helen. The two women attended Boston College together, and Colleen had introduced Doug and Helen. The families remain close and vacation together.

“He’s been ready for this for quite some time,” Marrone said Friday. “I’m excited for him.”

The O’Briens have two sons, Michael, 6, and Jack, who was born with lissencephaly, a rare genetic brain malformation that inhibits development.

“That’s been a big part of his life,” Friedgen said. “Boston was a very good place for his son for medical reasons, and I’m sure Penn State is going to be that way, too.”

O’Brien’s agent, Joe Linta, spent the last few days with O’Brien in State College, Pa., and said his client was ready to embrace the challenge.

“This was the opportunity of a lifetime for him,” Linta said.

“He’s unfazed by what’s happened,” he added, referring to the Sandusky scandal. “He’s sympathetic toward what happened to the victims. He’s proud to take on the challenge to restore the dignity to this place and restore it to where it’s been.”