Torn pectoral muscles are becoming the Vikings' Achilles' heel.
Reserve offensive tackle Carter Bykowski, an Eden Prairie native, is out for the season after surgery for a torn pectoral muscle. It's the team's fifth pectoral injury in the past 11 months.
The injury was confirmed by an NFL source Wednesday evening; Vikings coach Mike Zimmer said earlier Wednesday after practice that Bykowski had shoulder surgery, but did not provide a timetable for his return.
Four other Vikings — Brian Robison, Josh Robinson, Phil Loadholt and Brandon Fusco — have been sidelined in the past 11 months because of pectoral tears. Loadholt, the team's starting right offensive tackle, was put on injured reserve Tuesday because of a torn Achilles' tendon.
Zimmer addressed the team's problems with pec injuries earlier this summer.
Bykowski, who was acquired during Week 15 last season from the 49ers practice squad, served as backup tackle during training camp. T.J. Clemmings and David Yankey worked with the second team at the tackle positions, and Zimmer said the Vikings have also thrown in rookie guard Austin Shepherd at tackle.
Zimmer also said defensive tackle Shamar Stephen had arthroscopic surgery on a knee, but should be ready for the team's opening game.
Zimmer said Stephen had a scope but didn't disclose which knee he injured. Stephen, who served as a backup nose and three-technique tackle last season as a rookie, entered training camp on the non-football injury list with a left knee injury.
