Updated: 3:41 p.m.
Carriker suffered a torn quad tendon near the base of his right knee, Shanahan said. Orakpo has a torn left pectoral muscle, the the same muscle that he tore at the end of last season and had surgery on.
Shanahan said defensive end Doug Worthington will be activated off of the practice squad. He said Jarvis Jenkins takes over as starter for Carriker. And Rob Jackson will take over for Orakpo.
Shanahan said that Carriker will have surgery and will need five months to recover and that Orakpo will require surgery and will need roughly four months to return to full strength.
Shanahan expected both surgeries will take place some time next week.
Carriker last season recorded 34 tackles and a career-high 5.5 sacks. Meantime, Orakpo led the team with nine sacks, and also recorded a career-high 59 tackles and three forced fumbles.
Defensive end Jarvis Jenkins, the team’s second-round pick in 2011 who missed all of last season because of a torn ACL, will attempt to replace Carriker, and at outside linebacker, Jackson and Chris Wilson will compete to replace Orakpo.
“You have guys like Jarvis Jenkins that now gets his opportunity to start,” Shanahan said. “A year ago, we lost Jarvis and Adam took over and did a great job last year, played at a very high level. Jarvis will get his opportunity, guys like Kedric Golston, Chris Baker. You’ve got a guy like Doug Worthington, who has been on the practice squad and he gets activated. … At the outside linebacker spot you’ve got guys like Rob Jackson and Chris Wilson, who have to step up and play at a very high level, because we all know what ‘Rak has done for our defense and how well he’s played. We’ll get a chance for both of those guys to play at that position, and hopefully play very well.”