On Day 1, Bills Seek Williams and the Dolphins Trade Marshall

Linebacker and defensive end Mario Williams, a former first-round pick of the Houston Texans who is considered the best defensive player available among the 532 free agents, arrived in Buffalo less than two hours after free agency began at 4 p.m. Eastern, with the Bills expected to try to keep him from leaving without agreeing to a contract.

Moments after free agency began, the made a surprising move, acquiring the Pro Bowl receiver Brandon Marshall in a trade with Miami. The gave up two second-round draft picks to acquire Marshall from Denver two years ago, but received two third-rounders from the Bears.

The move leaves the Dolphins and their new coach, Joe Philbin, with no No. 1 receiver. The Dolphins are in the market for a new starting quarterback — they have met with Manning — but it also removes the headache of Marshall’s complaints about quarterbacks while Philbin incorporates a new system.

The trade reunites Marshall with Jay Cutler. Marshall and Cutler worked well together in Denver from 2006 to 2008, and they are joined in Chicago by Jeremy Bates, who worked in Denver and is now the Bears’ quarterbacks coach.

The Washington Redskins, who moved into the second overall draft spot to take Baylor quarterback Robert Griffin III, were trying to sign almost everyone else in what has become their annual — and all-too-often fruitless — cannonball into free agency. They overhauled their receiving corps even though the N.F.L. has docked them $36 million in cap space over the next two years because of what the league said were improperly structured contracts during the 2010 uncapped season.

First, they reeled in the former Indianapolis receiver Pierre Garcon, who will provide a speedy downfield — though drop-prone — threat. Fox Sports reported that the five-year contract includes a staggering $21.5 million in guaranteed money, which puts him behind the $24 million in guarantees Santonio Holmes got from the Jets, remarkable for a player who has never had a 1,000-yard season.

The Redskins also negotiated with the former San Francisco receiver Josh Morgan and the former Broncos receiver Eddie Royal.

While the Redskins were remaking their offense, New Orleans was making sure its powerhouse unit stayed largely intact, signing receiver Marques Colston to a five-year deal before free agency began.

The Tampa Bay Buccaneers, who must try to compete with the Saints in the N.F.C. South and who have a whopping $45 million in salary-cap space, signed the former San Diego receiver Vincent Jackson to a five-year deal, giving quarterback Josh Freeman the option he needs to continue to develop.

The most intriguing signing, though, may have been the one that happened nearly 24 hours before free agency began. , who did not play last season, signed a one-year contract with the late Monday night after a workout in which he caught passes from Coach Jim Harbaugh.

In 2010, an unhappy Moss was with three teams and caught only 28 passes. But Moss has apparently retained his speed, and if he remains healthy and committed to playing hard, the low-risk contract — there was no guaranteed money — provides the 49ers and the likely starting quarterback Alex Smith with the vertical threat their passing game lacked in 2011, when they lost the N.F.C. championship game to the Giants.

THOMAS STAYS WITH JETS The Jets re-signed the outside linebacker Bryan Thomas for another year. The team selected Thomas in the first round of the 2002 draft. Thomas, 32, missed the final 12 games last season after tearing his Achilles’ tendon on Oct. 2. No one from a group including Josh Mauga, Garrett McIntyre and Jamaal Westerman distinguished himself as a replacement.

Retaining Thomas, 32, should not preclude the Jets from pursuing additional help at the position, and they could make a play for Jarret Johnson, a longtime favorite of Coach Rex Ryan’s from Baltimore. BEN SHPIGEL

Lions Beat the Bears to Go to 5-0

The Lions (5-0) are undefeated through five games for the first time since 1956, the year before their last N.F.L. title. The defending N.F.C. North champion Bears (2-3) are off to their worst start since 2007.

Detroit and its fans were clearly fired up for the franchise’s first Monday night game in a decade. The Lions had their largest crowd at Ford Field, and the 67,861 fans created enough noise to rattle the Bears into nine false starts.

Chicago quieted the fans briefly by taking a 10-7 lead just before halftime and seemed to make them a little nervous by pulling within 8 points with 4 minutes 7 seconds left to play.

Best, though, made them roar again with a 43-yard run capped by a horse-collar penalty that gave Detroit the ball at the Chicago 22. He ran for another first down that took time off the clock and set up Jason Hanson’s 31-yard kick with 1:56 to go.

Stafford lofted a pass to Calvin Johnson for a 73-yard score — extending his N.F.L.-record start with nine touchdown catches in five games — early in the second quarter.

Best’s 88-yard run was the second-longest in franchise history, trailing only Bob Hoernschemeyer’s 96-yard run against the New York Yankees on Nov. 23, 1950.

Stafford was 19 of 26 for 219 yards with two touchdowns, including the go-ahead score to Brandon Pettigrew from 18 yards with 9:55 to go in the third quarter. Best more than doubled his career high with 163 yards rushing on 12 carries.

Jay Cutler was 28 of 38 for 249 yards with a touchdown and no interceptions for the Bears. Matt Forte ran for 116 yards.

LOSE WILLIAMS The Houston Texans lost outside linebacker Mario Williams for the season with a torn pectoral muscle. Williams appeared to sustain his injury while sacking Oakland’s Jason Campbell with about five minutes left in the first quarter of Sunday’s 25-20 loss.

The top overall pick in the 2006 draft, Williams moved from defensive end to outside linebacker this season in the new coordinator Wade Phillips’s 3-4 alignment. Williams was growing into the role more each week, and had five sacks and a forced fumble before the injury.

PACKERS’ CLIFTON INJURED Green Bay Packers Coach Mike McCarthy says the veteran left tackle Chad Clifton has a “significant” hamstring injury after leaving Sunday night’s game against the Atlanta Falcons. The team has not established a timeline for Clifton’s return, but Clifton seems likely to miss multiple games.

49ER NEEDS SURGERY San Francisco 49ers wide receiver Joshua Morgan will miss significant time with a broken bone in his lower right leg that requires surgery. He was injured late in the fourth quarter of San Francisco’s 48-3 victory against Tampa Bay on Sunday.

BILLS’ JONES SIDELINED Buffalo Bills receiver Donald Jones will miss four to six weeks with a sprained left ankle, and starting defensive tackle Kyle Williams’s status is uncertain for the team’s game at the Giants this weekend.