Buffalo underwent a regime change during the offseason with head coach Sean McDermott and general manager Brandon Beane replacing Rex Ryan and Doug Whaley, respectively.
The moves Friday are a clear sign the Bills are going to retool the roster with a new vision, but it could take some time to complete the process. Going from Watkins to Matthews, and Darby to Gaines is a downgrade in upside at each position, but the team did get draft picks it hopes will offset the difference.
Adam Caplan of ESPN provided some further background information on the swap:
Matthews has registered 225 catches for 2,673 yards and 19 touchdowns across three seasons since the Eagles selected him in the second round of the 2014 draft. That includes a 2016 campaign where he tallied 73 grabs for 804 yards and three scores.
Meanwhile, Darby enjoyed a strong rookie season after the Bills took him with the 50th overall pick in 2015. He racked up 68 combined tackles, 21 passes defended and two interceptions. He struggled to match that production last year, however, with just 12 passes defended and no picks.
Matthews should slide into the Bills' starting lineup opposite rookie wideout Zay Jones with recent signing Anquan Boldin operating out of the slot. The same goes for Darby, who could even emerge as the Eagles' top corner ahead of Jalen Mills and former Bills teammate Ron Brooks.