No terms were announced by the team, but NFL.com's Albert Breer reported the deal as a five-year extension worth $66 million. Matthews tweeted a picture of himself signing the contract Wednesday.
"Congratulations to Clay, who has quickly developed into a core member of our team," McCarthy said. "His accomplishments and the example he sets on and off the field will be vital to our continued success. We look forward to the rest of his Packers career."
Matthews' extension is worth just more than $13 million per year, lining up with what Rapoport predicted earlier in the week. Rapoport later reported, via a source who has seen the contract, that Matthews received a $20.5 million signing bonus. The extension makes Matthews the highest-paid linebacker in the NFL.
Rodgers is expected to become the highest-paid player in the NFL, and Matthews -- the Packers' first-round draft pick in 2009 -- has been liquid gold from the outset.
In 55 starts over four seasons, Matthews has tallied 42.5 sacks, including 13.5 during Green Bay's Super Bowl campaign of 2010 and another 10 last season. ProFootballFocus graded Matthews second among all 3-4 outside linebackers in 2012 and the most terrorizing pass rusher of the group. Matthews also was effective as a run-stopper and gives the Packers' hot-and-cold defense its most reliable cornerstone.
Tom Silverstein of the Milwaukee Journal Sentinel reported over the weekend that the Packers "likely" would announce both contracts simultaneously. If there's a holdup on the Rodgers deal, it shouldn't take long before he's also under lock and key, giving the Packers two superstars to build around on both sides of the ball.