JACKSONVILLE, Fla. -- The Jaguars' first victory of 2014 turned out to be a costly one: They lost two defensive starters, including middle linebacker Paul Posluszny for the season with a torn pectoral muscle.

Defensive end Andre Branch also will miss at least six weeks after tearing a groin muscle, but it's the loss of Posluszny -- who will be placed on IR and is scheduled to have surgery this week -- that really hurts the Jaguars (1-6).

Not only is he the Jaguars' leading tackler (69) and best defensive player, he's also responsible for making the defensive calls and is one of the team's leaders.

Tackling Machine The Jags' Paul Posluszny, who is lost for the season with a torn pectoral muscle, has been the league's most prolific tackler since 2008. Player Tackles Paul Posluszny 860 London Fletcher 827 Chad Greenway 818 ESPN Stats & Information

"It's tough because he is talented and he is a captain of our team and a leader," coach Gus Bradley said Monday afternoon. "To downplay that part of it wouldn't be fair to him. Important part, but I do believe that we'll have guys step up and move on."

Posluszny is in his fourth season with the Jaguars and eighth overall. The 2013 Pro Bowler has recorded at least 110 tackles every season from 2008 to '13. He was second in the NFL with 162 tackles in 2013.

Branch was a second-round draft pick in 2012 and has 10 sacks in his career, including six in 2013. He has three sacks, two forced fumbles and 13 tackles this season. If he is able to return in six weeks, his first game back would be against the Houston Texans on Dec. 7.