NEW YORK (AP) — The NFL can increase the six-game suspension for Pittsburgh Steelers quarterback Ben Roethlisberger if new evidence of misbehavior emerges that violates its personal conduct policy.

Commissioner Roger Goodell handed down the punishment after prosecutors decided not to charge Roethlisberger in a case involving a 20-year-old college student who accused him of sexually assaulting her in a Georgia nightclub last month. Roethlisberger also must undergo a comprehensive behavioral evaluation by professionals.

Goodell said Friday at his annual session with Associated Press Sports Editors that the conduct policy allows him to revisit the ban, announced earlier this week. If evidence of other incidents is presented, "the penalty still has some flexibility," Goodell said.

In explaining why he acted even though no criminal charges were filed against the quarterback, Goodell said:

"It's my responsibility to protect our reputation and our integrity. That's what the personal conduct policy is; we all have to be held to a higher standard. It specifically states you don't have to violate the law if there is a pattern of behavior.

"We go back through all the incidents and try to understand is there is any kind of pattern, and we have enough information to believe he's not making sound judgments at critical points."

A two-time Super Bowl winner, Roethlisberger also is being sued by a woman who accused him of raping her at a Lake Tahoe hotel-casino in 2008. He denied the allegation and wasn't charged. He is the first player suspended by Goodell under the conduct policy who hasn't been arrested or charged with a crime.

"First, as a league, we rely on our credibility for acceptance with our public," Goodell said. "The integrity of the game and people participating in it is a critical element.

"Second, protection of our brand. It reflects poorly on our brand.

"That's why everyone came together to strengthen our policy years ago to make certain we keep that high standard."

Roethlisberger, who stands to lose more than $2.8 million in salary, can't attend team activities until he has been cleared by the league, based on the outcome of his evaluation.

Goodell also said:

—A labor agreement with the players is essential for the sport to grow. He cited the lack of new stadium projects since the current collective bargaining agreement was reached in 2006, just before he replaced Paul Tagliabue as commissioner.

The owners opted out of that deal two years ago, and a work stoppage is possible in 2011; the contract expires in early March.

Any new CBA could include a salary cap or have a setup similar to this season, in which there is no cap and free agency for veterans begins after six seasons.

—Expanded rosters have been discussed with the union should the regular-season schedule be stretched to 18 games. Two preseason games would be dropped. However, everything is dependent on a new contract.

—The league is considering developing better pads for players. In recent years, he said players were wearing less padding and defensive lineman might be using quarterback pads, which are smaller and often not as protective. Goodell has spoken with NFLPA executive director DeMaurice Smith about the issue.

He also expressed concern about properly fitting helmets, noting that the league addressed the issue of improperly fastened chinstraps a few years ago because too many helmets were flying off players' heads.

—The NFL will continue to be proactive in dealing with concussions, keeping a "very conservative approach" to when a player is allowed to return to action.

"Medical will always override competitive issues," he said.