The hows and whys of Bill O'Brien's early departure from Penn State will be debated and discussed for months.

But in the meantime, there's one simple and overriding reason why O'Brien made the jump back to the NFL.

“I missed it,” the ex-Nittany Lions coach said.

That truth was spoken not in State College, but in O'Brien's new home in Houston on Friday as he was officially introduced as the new head coach of the Texans.

Though O'Brien has spent most of his coaching career working in college, he fell in love with the pro game during his extended stint with the New England Patriots. In the days since news broke that O'Brien would leave Penn State after just two years, Lions players and coaches have all mentioned that a return to the NFL was O'Brien's dream.

Naturally, O'Brien is well aware that he leaves some hard feelings in his wake, particularly amongst a Penn State fanbase that has repeatedly had its emotions shredded over the past two-plus years.

“I want to thank Penn State,” O'Brien said. “I love the players at Penn State and respect their toughness and resiliency. I do regret not being able to continue with the great kids on that team.

“I never tried to mislead anyone. But I understand if some people feel let down.”

O'Brien and the Texans had been in discussions over the past two weeks, and up until the start of this week, it still appeared as though O'Brien would return to Penn State.

The value of the contract has not yet been disclosed, but O'Brien is expected to receive a notably higher salary than most NFL rookie head coaches. That figure will likely include the roughly $6.5 million that O'Brien owes Penn State for leaving with three years left on his deal with the school.

He had operated as though he would still be at Penn State in 2014 since the start of the offseason, making changes to his coaching staff, hitting the road recruiting and working to convince star receiver Allen Robinson — who declared for the NFL draft on Thursday — to return for his senior season.

The lure of the NFL and the opportunity to focus more on football and not be the face of an entire university, however, was stronger.

“I believe that Bill O'Brien was presented with just a tremendous opportunity that was one that, for his family and his future, he just could not pass up,” Penn State athletic director Dave Joyner said. “So I believe he always had Penn State's best interests at heart and this is just something that came up that he couldn't pass up. We wish him well.”

Houston and owner Bob McNair had reportedly set a New Year's Day deadline for a decision from O'Brien, who was weighing his options up until Tuesday night. ESPN was first to report that O'Brien had accepted the Texans' offer less than two hours before 2014 began.

It wasn't an easy choice.

Penn State interim coach Larry Johnson said Friday that O'Brien was “very emotional” when he talked to him after picking the Texans.

“It was a good, personal conversation,” Johnson said. “When you build a relationship like (O'Brien had with Penn State), you don't just walk away with it. He cares.”

As for the players O'Brien leaves behind?

“I think they're excited for Coach O'Brien,” Johnson said. “I think they understand that this is a business, but also that it's a great opportunity for his family. His life's dream is to go back to the NFL as a head coach and our players understand that. And all of them wish him very well moving forward.

“He's talked to every player, which I think is really great.”

If Penn State can continue it's surprisingly quick rise from the ashes under a new head coach, O'Brien will deserve much of the credit for leading the program through its darkest period.

Regardless, there's no question that O'Brien himself can credit his own rise to the top of his profession to the Lions.

“Yes,” O'Brien said. “I owe a lot to Penn State.”