PHILADELPHIA (AP) — With perhaps billions of dollars stake, a hearing Tuesday over concussion litigation filed against the NFL promises to be a brawl between legal heavyweights.

About 4,200 former players have sued the league. Some are battling dementia and depression. Others simply want their health monitored.

And a small number, like 12-time Pro Bowler Junior Seau, have committed suicide. The players' lawyers accuse the NFL of hiding known concussion risks.

They hope to keep the litigation in federal court, and obtain NFL documents to learn what the league knew when.

The NFL says the complaints belong in arbitration under the collective bargaining agreement.

NFL lawyer Paul Clement (kluh-MENT') has fought gay marriage, gun-control measures and health care mandates before the Supreme Court. Players' lawyer David Frederick is best known for taking consumer protection fights to the high court.

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