WASHINGTON — The head of the NFL Players Association said Tuesday his union has differences with the NFL over how to address head injuries suffered during pro football games, but they're not fighting about it.

One day before a congressional hearing about head injuries in professional football players, union head DeMaurice Smith credited the NFL for doing a "tremendous job" to improve player safety in the past five years.

"This is not a battle between us and the league," Smith said.

But he also complained that he didn't have access to the medical information the NFL collects on its players. That information, he said, can be used "to come up with better, safer ways to not only deal with their exposure to injury on the field, but also to improve their lives off the field."

NFL spokesman Greg Aiello said he wasn't aware of any medical information the league isn't sharing with the union.

"We share a great deal of medical information with the union, and the players have full access to their medical records," Aiello said in an e-mail to The Associated Press.

Smith will testify along with NFL commissioner Roger Goodell; Rep. Bill Pascrell, a New Jersey Democrat and co-chairman of the Congressional Brain Injury Task Force; medical experts and former players, including former New York Giants running back Tiki Barber.

Among the medical experts testifying are researchers from the Boston University School of Medicine, who announced last week that a football player who never competed beyond the college level — former Bingham High School and Snow College player Mike Borich — suffered from a degenerative brain disease previously discovered in former NFL players.

The hearing will look at the lasting impact of head injuries, how to limit them and how to compensate players and their families. A preliminary study done for the NFL suggested retired pro football players may have a higher rate than normal of Alzheimer's disease or other memory problems. Lead author David Weir, who is among the witnesses for Wednesday's hearing, has said the results show the topic is worth further study but they do not prove a link between playing football and later mental troubles.

When the study was released, the NFL said further study is already under way and stressed that memory disorders affect many men and women who never played football or other sports.

Dr. Thom Mayer, the union's medical director, said at the news conference that football is a sport where 100 percent of the participants will get injured.

"Not everyone has a head injury, but it's common enough that it's the thing that we're most concerned about," he said.

Mayer said that rules changes and improvements in helmet technology have helped, but he'd like to see further improvements in how to handle players both immediately after and in the days following a concussion, and in decisions on when to return to play.

"It's an ongoing battle — not between us and the NFL — but between what we know and what we don't know in order to protect our players," he said, adding that he was confident that the sport will get to a point where head injuries will be far less dangerous.

"No one is saying we should ban football — at least not yet," Smith said. "But why can't we have a great game that's safe for our players? Why can't we live in a world where the National Football League becomes the standard bearer on this issue?"

On the labor front, Smith he's proposed to the owners that if there isn't a deal on a new contract by the middle of January, the two sides should conduct five days of concentrated meetings.

Aiello, the NFL spokesman, responded that the league will meet with the union "as often as we can" to get a deal.QB CONTROVERSY FOR TITANS?:Jeff Fisher has stayed away from a quarterback controversy all through the Tennessee Titans' dreadful start.

Now, team owner Bud Adams reportedly wants a change.

Adams informed Fisher he wants Vince Young to start over Kerry Collins this weekend against Jacksonville, according to the Tennessean. The Nashville newspaper cited sources Tuesday that Adams apparently told Fisher his preference after the Titans lost to New England 59-0 on Oct. 18 and became more insistent during the bye week.

A call to Adams' Houston office was referred to the team's media relations department in Nashville. A message was not immediately returned Tuesday. Fisher declined Monday to say who his starter will be Sunday for "competitive reasons."

EX-JAGUARS' PLAYER TESTIFIES IN SHOOTING: Former Jacksonville Jaguars offensive lineman Richard Collier tried to duck away from the rapid burst of bullets that left him paralyzed, he testified Tuesday at the trial of the man accused of shooting him.

Collier said he was sitting in the passenger seat of his sport utility vehicle talking and listening to music with recently cut teammate Kenny Pettway. The car was running and the back door was left open while a woman he met earlier that night went inside her apartment.

"There was a line of gunshots coming from behind me," said Collier, sitting in a wheelchair in front of the jury box. "I was telling Kenny to drive. I didn't know if I was getting hit or not, I couldn't feel it. Shots kept coming."

But he said Pettway panicked and didn't move the SUV. The next thing he remembered was being in an ambulance. He never saw the shooter. Neither did Pettway.

Prosecutor Bernie de la Rionda told jurors Tyrone Hartsfield was the person who shot Collier in a cowardly act of revenge in September 2008, while defense attorney Ann Finnell told jurors that the player had many enemies and police didn't investigate all of them.

Collier recalled the first time he saw Hartsfield, five months before the shooting. He said they were at another club and Hartsfield refused to get out of the way as he tried to leave. Collier said Hartsfield shoved him, and he pushed back, causing a drink to spill in Hartsfield's face.

"He had a snarl on his face, his fist balled up," Collier said. "He looked like he wanted to hit me, so I hit him first."

Collier, then 6-foot-7 and 350 pounds, said he punched Hartsfield three times in the face, knocking him to the ground. He said he never saw him again, but that a friend told him the night of the shooting that Hartsfield was also in the club.

"You weren't worried about him, were you?" Finnell asked.

"No, I had let it go. I was through with it," Collier said.

Hartsfield never let it go, de la Rionda said in his opening statement. He carried a grudge for months. When Hartsfield saw Collier at the nightclub, he began calling friends to get a gun and then waited for the right chance to use it.

"Revenge, payback," de la Rionda shouted in his opening arguments. "When this man before you ... pulled a trigger and repeatedly shot a defenseless man, he was getting his revenge."

Collier was shot several times and left paralyzed from the waist down. His left leg was amputated. Police used cell phone records to build a case against Hartsfield, who had given police his number after reporting the first altercation.

Hartsfield slowly shook his head several times during de la Rionda's opening statement. The prosecutor said Hartsfield found out where Collier lived and went out looking for him. So when he saw Collier again at another nightclub, he set a plan in motion.

"When the defendant saw his target, Richard Collier, he wanted a gun and he set in his mind what he then did," de la Rionda said. "He wanted the perfect opportunity."

A cousin provided a gun, and later Hartsfield and his friend, Stephfan Wilson, followed Pettway and Collier as the players followed two sisters back to their apartment, de la Rionda said. The women went into the apartment. Jemelia Corbie returned, then went back inside again, leaving the back door open.

De la Rionda said police found Wilson through Hartsfield's phone records. Wilson told police Hartsfield got out of their car by the apartments, he heard the shots and then Hartsfield came back and they drove away.

Finnell said the case isn't about revenge, but about greed, saying Wilson was on probation for a bank robbery and was trying to avoid going back to prison. Another witness wanted reward money, she said.

"Wilson knew what he needed to do to save himself — he told them exactly what they wanted to hear," Finnell said. "He told them Tyrone Hartsfield was bent on revenge."

She said there are no credible witnesses placing Hartsfield at the shooting, nor any physical evidence tying him to the shooting. She asked Collier and other witnesses about other women Collier had dated, including more than one at once.

The sisters also testified that they heard Collier tell Pettway that he didn't know why he had so many enemies, but that the comment came in reference to seeing Hartsfield again.

JOHNSON APOLOGIZES TO CHIEFS — AGAIN: Kansas City Chiefs running back Larry Johnson issued his second apology in 12 months Tuesday and was told to stay away from the team while the NFL and the Chiefs complete their investigation into his use of a gay slur.

As Johnson was releasing his apology, a national gay rights advocacy organization called on the league and the team to take disciplinary action against the two-time Pro Bowler.

The latest chapter in Johnson's stormy career began Sunday night when he questioned coach Todd Haley's football credentials on his Twitter account.

He used the slur during an exchange with one of his Twitter followers. A day later, he used it again as he brushed off reporters and told them he would not comment, according to the Kansas City Star, which recorded the comment.

Haley refused to address the matter Tuesday, saying it was still being investigated.

"I'm just not going to comment any further because there is some stuff going on," Haley said.Johnson, who turns 30 next month, signed a five-year contract extension in 2007 that included $19 million guaranteed and could be worth up to $45 million. The team could be checking to see whether Johnson violated contract provisions that would allow the Chiefs to cut him with reduced financial obligation.

Last spring, an arbitrator ruled that the Chiefs could release the running back and not owe him $3.5 million in guaranteed money because he had violated contract conditions by pleading guilty to disturbing the peace in another incident.

The issue became moot when the team elected not to cut him and until he began tweeting on Sunday night, the often-volatile Johnson had been on good behavior.

The Chiefs said they have told Johnson he would not be allowed to practice with the team or participate in team activities until the matter was resolved, though he has not been suspended. NFL spokesman Greg Aiello said the league would have no comment pending the investigation.

Johnson, who needs only 75 yards rushing to become the Chiefs' all-time leader, apologized to Haley, the team, fans and the league "for the words I used."

"I regret my actions. The words were used by me in frustration, and they were not appropriate," he said through a spokesman. "I did not intend to offend anyone, but that is no excuse for what I said."

The apology sounded similar to one he made almost exactly a year ago after one woman accused him of throwing a drink on her and another said he had pushed her. The incidents happened separately in Kansas City nightclubs and led to his being sentenced to two years' probation after pleading guilty to two counts of disturbing the peace.

"I'm going to work to that point to get my life back on track and know that I and I alone put myself in these critical situations and environments to where things don't come out favorably to me," he said on Oct. 22, 2008.

At the time, Johnson was benched for three games by then-coach Herm Edwards and suspended for a game by commissioner Roger Goodell.

On Tuesday, Johnson apologized to "all the kids who view athletes as role models. I was not a good role model yesterday and hopefully I can become a better role model. We all make mistakes, and the challenge is to learn from them.

"I will do my best to learn from this one as I move toward becoming a better person, teammate, and member of the Kansas City Chiefs team and community."

Johnson's agent said all his client could do now was wait.

"It's up to the NFL to investigate it and see what they want to do, and we will respond accordingly," Peter Schaffer told The Associated Press. "We've apologized. Larry's trying to move forward. It is what it is right now."

Jarrett Barrios, president of the Gay & Lesbian Alliance Against Defamation, called on the NFL and the Chiefs to take disciplinary action and seize a chance to educate "on the dangers of homophobia in sports."

Such slurs are used to "ridicule and harass young gay and transgender athletes on local sports fields across America," Barrios said.

Barrios said he welcomed the apology.

"Larry Johnson's apology sends an important message that there is no excuse for using anti-gay epithets," Barrios said.

Drafted in the first round out of Penn State in 2003, Johnson was one of the best running backs in the NFL in 2005 and '06, rushing for more than 1,700 yards in each season. This year, like the Chiefs, he has struggled, averaging only 2.7 yards per carry.

Kansas City (1-6) has a bye week.

HASSELBECK'S DAUGHTER INURIED IN ACCIDENT: The daughter of Seattle Seahawks quarterback Matt Hasselbeck is recovering after surgery to repair injuries sustained on a family trip to Central Washington over the bye weekend.

Hasselbeck posted on his Twitter site Tuesday he had the "worst bye week ever. 6 year old daughter got hit by a dirt bike."

The 34-year-old father of three said he spent his weekend at the hospital.

He thanked the dentist who repaired Mallory's mouth and the staff at Central Washington Hospital in Wenatchee. He also thanked the staff who treated Mallory at Seattle Children's Hospital upon the family's return home.

He said she will miss her basketball season but will recover.