(SportsNetwork.com) - As the start of a new league year brought a flurry of trades in the NFL, one of the biggest deals was finally announced by the teams involved.

The Buffalo Bills acquired former NFL rushing champion LeSean McCoy from the Philadelphia Eagles for linebacker Kiko Alonso, a deal that had been widely reported over the past week but was only made official on Tuesday afternoon.

The Bills announced that McCoy signed a contract extension, reported over the weekend to be a new five-year, $40 million deal with $26.5 million guaranteed.

The extension came amid reports McCoy was unhappy over his new destination.

McCoy, 26, was explosive in Chip Kelly's hurry-up offense, rushing for 2,926 yards and 14 touchdowns with 80 receptions for 694 yards and two scores over the past two seasons.

He led the NFL in both rushing yards and yards from scrimmage in 2013 but saw a dropoff in both categories last season.

McCoy set the Eagles' all-time career rushing record during the 2014 season. He gained 6,792 yards and scored 44 touchdowns on 1,461 carries in 90 games for the franchise, averaging 4.6 yards per carry.

Alonso, 24, missed all of last season after having surgery to repair a torn anterior cruciate ligament suffered during an offseason workout in Oregon.

The second-round draft pick led the Bills in tackles in 2013 as a rookie with 159. He had two sacks and four interceptions while starting all 16 games.