PHILADELPHIA — Lawyers for professional football players who reached a landmark settlement with the N.F.L. over concussions said Tuesday that hundreds of their clients may have been swindled by unscrupulous lenders and advisers looking for a cut of their payments.

In a hearing in federal court here, Christopher Seeger, a lawyer for the retired players who sued the N.F.L., said nearly 1,000 ex-players had signed dubious contracts with lenders and lawyers. Nearly a dozen lenders have lent money at interest rates of 50 percent or more to players who will pay them back with money they receive from the estimated $1 billion settlement, which provides up to $5 million to players with dementia, Parkinson’s disease and other serious neurological conditions.

In the last few months, players have also signed contracts with law firms and so-called claims service providers that promise to help players file settlement claims in return for 10 or 15 percent of any cash awards. Some of these firms work with the lenders as well as brokers, who receive fees for referring players.

“We don’t want to watch these awards be cannibalized,” Seeger told Judge Anita B. Brody of the United States District Court for the Eastern District of Pennsylvania, who is overseeing the settlement. Judge Brody had called the hearing in response to news reports, including those in The New York Times, of what she called “purportedly deceptive or misleading solicitations” of former players.