PHOENIX—NFL Commissioner Roger Goodell, in his first public comments on the controversy surrounding the New England Patriots’ use of under-inflated footballs during the AFC championship game, said Friday he has a “responsibility to protect the integrity of the game” and pledged that the league will continue to pursue its investigation of the incident vigorously but fairly.

“We want the truth,” Goodell said at his annual news conference two days before the Super Bowl. “That’s what I think our fans want. That’s what our clubs want. And so what we want to do is make sure that we find that truth. If there are violations of the rules, we take them seriously, particularly when they deal with the integrity of the game and the rules.”

Goodell conceded it has been “a tough year” for him and the league, beginning with the sharp criticism that Goodell received in September for the NFL’s handling of the Ray Rice, Adrian Peterson and Greg Hardy abuse cases. Goodell said he has learned difficult lessons during a humbling experience but reiterated he intends to remain on the job.

Responding to a question about whether he could imagine any set of circumstances that would lead to him resigning or being fired, Goodell said: “No, I can’t. Does that surprise you?

“Listen, it has been a tough year. It’s been a tough year on me personally. It’s been a year of, what I would say, humility and learning…. We take that seriously. It’s an opportunity for us to get better. It’s an opportunity for us, for our organization, to get better. So we’ve all done a lot of soul-searching, starting with yours truly. And we have taken action.”

A season that began amid turmoil for the NFL is ending the same way as Sunday’s Super Bowl matchup between the Patriots and Seattle Seahawks arrives. The league has determined that the Patriots used under-inflated footballs, in comparison to NFL specifications, in the first half of the AFC title game but has not determined whether that was done deliberately by the team.

“We take seriously anything that potentially impacts the integrity of the game,” Goodell said. “We are focusing principally on two questions: Why were some footballs used in the game that were not in compliance with the rules? And was this the result of deliberate action? I want to emphasize we have made no judgments on these points and we will not compromises the investigation by engaging in speculation.”

The Patriots have denied wrongdoing. They arrived in the Phoenix area Monday with their owner, Robert Kraft, expressing disappointment with the way the situation has been handled and saying his coach, Bill Belichick, and quarterback, Tom Brady, are owed an apology if the league’s investigation does not prove wrongdoing.

Kraft was not seen in the audience at Goodell’s news conference but his demand for a prospective apology was the subject of a question to Goodell.

“This is my job,” Goodell said. “This is my responsibility to protect the integrity of the game. I represent 32 teams. All of us want to make sure that the rules are being followed. And if we have any information where the potential is that those rules were violated, I have to pursue that. And I have to pursue that aggressively. So this is my job. This is the job of the league office. It is what all 32 clubs expect and I believe our partners and fans expect. We will do it vigorously and it is important for it to be thorough and fair.”

Goodell left open the possibility of tougher penalties being imposed if it is determined that the Patriots willfully violated league rules. In the aftermath of his 2007 ruling, in which Goodell fined Belichick and the Patriots a total of $750,000 and stripped a first-round draft pick from the team for improperly videotaping opposing coaching signals, Goodell wrote a March 2008 memo to the NFL’s competition committee pledging increased penalties for future competitive violations and proposing a lower threshold of proof to establish such violations. The owners endorsed those recommendations.

“The standards are always going to be evaluated,” Goodell said. “We will make sure that if the penalties that exist in any given circumstances don’t fit those violations, we’ll adjust that. We’ll increase them. That’s important for us to do as we continue to make sure that the league is run in an appropriate way and with great integrity.”

Goodell said that Seahawks tailback Marshawn Lynch was failing to fulfill his professional obligations by showing up at news conferences during Super Bowl week but refusing to answer questions from media members and saying that he was present only to avoid being fined.

“It is part of your job,” Goodell said. “And there are things that we all have to do in our jobs that we may not necessarily want to do…. I understand it may not be on the top of his list. But everyone else is cooperating. Everyone else is doing their part because it is our obligation.”

Goodell said the NFL plans to hire a chief medical officer soon and is close to adding a chief disciplinary officer as promised when the league announced its reworked personal conduct policy in December.

He said the league will consider implementing more difficult extra points and making a wider array of penalties potentially subject to instant-replay reviews. He said there are some reservations within the league to the proposal to expand the playoff field from 12 to 14 teams beginning next season.

“There are positives to it,” Goodell said. “But there are concerns as well, among them being the risk of diluting our regular season and conflicting with college football in January.”