The struggling Vikings defense will have to right the ship this season without linebacker Anthony Barr, who was placed on injured reserve Monday because of a season-ending torn pectoral muscle, coach Mike Zimmer said.

Barr, a 28-year-old Pro Bowl player and team captain, suffered the injury near the end of the first quarter of Sunday's 28-11 loss to the Indianapolis Colts. He came up clutching his right shoulder after tackling Colts running back Jonathan Taylor on a 5-yard catch, and seemed to play through the injury for one snap before leaving the game between the first and second quarters.

Barr joins defensive end Danielle Hunter on IR, leaving Zimmer to keep the defense together without another centerpiece.

"He's an integral part of the defense," Zimmer said Monday via videoconference. "Great leader, great guy. It's tearing him up inside that he's not going to be able to play, but it is what it is. We're going to move on."

Against the Colts, Barr was replaced by rookie Troy Dye, a fourth-round pick who missed some time in the second quarter because of an ankle injury of his own. The Vikings defense had some mixed signals without Barr, according to Zimmer, as communication duties shifted to Eric Kendricks, who took Barr's job of relaying play calls to the huddle.

"I thought Troy came in and did some good things," Zimmer said. "He had a couple missed tackles, but he ran pretty well. Once Barr went out, it got a little confusing because Eric [Kendricks] was trying to get the calls from the headset and then make the calls and get guys lined up, so that got a little confusing. [Eric] Wilson did fine. We still got a lot of things we got to work on with those guys, but we anticipate that they'll continue to get better."

Dye, or another linebacker, won't necessarily play the same role. Barr, a former UCLA edge rusher who has 423 career tackles, has been the Vikings' primary blitzing linebacker since he was drafted in 2014's first round. Zimmer now has to find other ways to ramp up pressure on passers. The Vikings have only two sacks this season, both in the second half Sunday against the Colts.

Next to Kendricks, Barr also formed a strong run-stopping tandem, but that unit has struggled in the first year without nose tackle Linval Joseph or his replacement Michael Pierce, who opted out. Only four NFL defenses — the Lions, Texans, Bengals and Dolphins — have allowed more than the 309 rushing yards surrendered by the Vikings in two games.

Barr, who will miss most of his seventh NFL season after playing in 87 of 98 regular season games, is part of a rash of notable injuries across the league in Week 2 games.

Giants running back Saquon Barkley (torn anterior cruciate ligament), Broncos receiver Courtland Sutton (ACL) and Colts safety Malik Hooker (Achilles' tendon) are done for the season. Seahawks linebacker Bruce Irvin tore his ACL and is out for the season. Colts receiver Parris Campbell (MCL/PCL) is likely done for the season after taking a low hit from Vikings safety Harrison Smith on Sunday. Panthers running back Christian McCaffery has a high ankle sprain that could sideline him up to six weeks. Broncos quarterback Drew Lock may miss up to five weeks with a severely strained rotator cuff in his throwing shoulder.

The San Francisco 49ers had a slew of injuries, and defensive linemen Nick Bosa and Solomon Thomas were both ruled out for the season with torn ACLs. The results were delayed Monday because a truck hauling the MRI trailer broke down Sunday night, according to head coach Kyle Shanahan.

Quarterback Jimmy Garoppolo and running backs Raheem Mostert and Tevin Coleman were also injured in a road win over the Jets, after which Shanahan said players raised concerns about MetLife Stadium's "sticky" turf. San Francisco is scheduled to return to MetLife Stadium on Sunday to play to the Giants.