The Washington Redskins agreed to terms with two-time Pro Bowl strong safety Brandon Meriweather on Thursday, filling the void created by the expected departure of LaRon Landry.

The 5-foot-11, 190-pound University of Miami product agreed to a two-year, $6 million deal, according to one person familiar with the deal.

The signing is the third for the Redskins since free agency began Tuesday at 4 p.m., despite a reduction in salary cap space of at least $18 million this year. That move was mandated by the NFL as a penalty for the way Washington structured some player contracts in 2010, when the league had no salary cap.

The Redskins have been considering a challenge to the NFL’s ruling, but may have to go it alone if they do. The Dallas Cowboys, who lost $10 million over two years in the same decision, are unlikely to challenge that decision, a person familiar with the case said Thursday.

It remained unclear Thursday whether the Redskins would contest the league’s decision, either via an appeal to the NFL or a legal challenge. The team declined to comment.

The person with knowledge of the case said the Cowboys probably would do nothing but that the Redskins “might be considering some legal options.” But the Redskins might not “want to take that on” because of the possible ramifications of challenging a league decision in court, the person said.

The Redskins risk further alienating other teams and league officials, the person said. Another person familiar with the case has said that some in the league were angry enough about the Redskins’ actions that they had urged NFL Commissioner Roger Goodell to strip the team of some draft picks. Instead, the league decided to reduce the Redskins’ salary cap space by $36 million over two years.

The league concluded that the Redskins and Cowboys attempted to gain an unfair advantage by the way they structured players’ contracts in 2010, when the sport had no salary cap. However, the teams technically committed no violation of salary cap rules.

Both teams have denied wrongdoing. The Redskins, in a written statement earlier this week, said they complied with the NFL’s labor contract and noted that all their player contracts were approved by the league office.

In other free agent moves Thursday, wide receiver Eddie Royal agreed to a contract with the San Diego Chargers, two days after his near-deal with the Redskins unraveled.

The Chargers announced Royal had agreed to a three-year contract but did not immediately disclose the financial terms. One person close to the negotiations said the contract is worth a little more than $13 million, including $6 million guaranteed.

The Redskins had believed Tuesday, on the opening day of free agency, that they had a two-year deal with Royal, thought to be worth up to $12 million, basically in place. Royal had even texted a Redskins player on Tuesday about his plans to come to Washington. But the Redskins were unable to apply the official finishing touches to the deal and other teams became involved in the bidding.

Meriweather started four games at free safety for the Chicago Bears last season, playing in 11 total and recording 32 tackles. But he struggled in coverage and was demoted. Because of his strengths as a run-stopper, Meriweather is considered a more natural fit at strong safety.

Before last season, Meriweather — the 24th overall pick of the 2007 draft — spent four seasons with the New England Patriots. His best season came in 2009, when he started all 16 games for the Patriots and recorded 83 tackles and five interceptions. He made the Pro Bowl that season, and again in 2010 after a 68-tackle, three-interception campaign.

But Meriweather, who at times was guilty of questionable decision-making in coverage and hurt his team with poor tackling, didn’t survive New England’s final round of cuts in September 2011. He signed with the Bears shortly thereafter.

Finding a strong safety ranked among the Redskins’ top priorities on defense. It’s expected that they will let Landry, who ended the last two seasons on injured reserve with a strained Achilles’ tendon, depart via free agency. The team already has reached deals with free agent wide receivers Pierre Garcon and Josh Morgan, and may try to add a free safety after releasing Oshiomogho Atogwe on Monday. It also is looking for help on the offensive line.