Flanagan's new deal is through the 2005 season and includes a $2.5 million signing bonus, according to the Green Bay Press-Gazette. Rivera, 29, also received a $2.5 million signing bonus.
Flanagan, 28, was scheduled to become an unrestricted free agent at the end of this season. The Packers currently have 11 players, including starting left guard Mike Wahle, who are scheduled to become unrestricted free agents, meaning they can sign with any team.
Other players who will become unrestricted free agents include wide receivers Bill Schroeder and Corey Bradford.
The Packers drafted Flanagan with the first pick of the third round in the 1996 NFL draft. But Flanagan suffered two broken bones during a preseason game of his rookie season and was hindered by complications from the injury over the next two seasons. Despite extensive rehab, Flanagan worked his way onto the active roster in '98 and played backup to Frank Winters in '99 and 2000.
Packers director of player finance Andrew Brandt said recently that he wanted to sign at least one player to a contract extension this season.
"Extensions during the season are tough because you want to preserve cap room as much as possible in case of injuries or unplanned emergencies on the roster, plus you want to have a little more time to evaluate players before you jump into a new contract," Brandt said.