EDEN PRAIRIE (AP) — When Carter Bykowski went down with a torn pectoral muscle this week, it not only depleted the Minnesota Vikings’ depth on the offensive line.

It also underscored a problem the Vikings have been trying to diagnose since earlier this summer.

Bykowski, a backup on the offensive line, is the fifth Vikings player to suffer a pectoral injury in the past year. When training camp opened at the end of July, coach Mike Zimmer said the team was trying to examine why so many players have suffered the same injury.

“It’s a combination of things, really,” Zimmer said on Thursday. “It’s dehydrated muscles. It’s getting in the position. Sometimes it’s over-strengthening. Sometimes it’s fatigue. Still, we’re calling around to every expert that we can find and keep digging.”

Bykowski joins defensive end Brian Robison, defensive back Josh Robinson, right tackle Phil Loadholt and right guard Brandon Fusco on the list of players to injure a pectoral muscle.

Zimmer said Thursday it was still too early to say if Bykowski will be put on the season-ending injured reserve list. But the injury typically requires months of recovery time.

Loadholt missed the last 11 games with the injury last season. After rehabbing and returning to action fully healthy in training camp, he tore his left Achilles tendon early in the preseason game against Tampa Bay last weekend, ending his season.

Loadholt returned to team headquarters on Thursday, and Zimmer said he would rely on the veteran tackle to be another coach for a young group of offensive linemen trying to fill the void created by his absence.

“He obviously was devastated when it happened, but I think he’s starting to understand that now he’s got to get back,” Zimmer said. “I told him he will be one of many guys that have had Achilles that have come back that I’ve had before. We expect him to have a good recovery.”

Rookie fourth-round draft pick T.J. Clemmings has been elevated to the starting spot at right tackle and the Vikings will watch the waiver wire and free agency going forward to see if they can add more bodies to bolster the depth on the line. Zimmer said the team is looking for a player who can play both tackle spots to give them a little more flexibility with roster construction on game days.

Youngsters Tyrus Thompson and Austin Shepherd could be candidates for that swing role. But both are rookies, so the Vikings could be in the market for a more experienced player to stabilize that spot.

Minnesota holds its preseason home opener on Saturday against the Oakland Raiders and second-year linebacker Anthony Barr plans to debut after missing the first two preseason games. Barr was working his way back gradually from a knee injury that cut a promising rookie season short last year, but Zimmer said he’s ready to go now.

“He told (head athletic trainer Eric Sugarman) that he feels the best he’s felt in a long, long time, right now,” Zimmer said. “He’s having fun at practice. He’s excited to get going and now we can start implementing him into things a lot more.”