Jonathan Cooper suffers broken leg

The Arizona Cardinals' plan to revamp its offensive line appears to have hit a huge road block Saturday as rookie Jonathan Cooper suffered a broken leg in a 24-7 preseason loss to the San Diego Chargers.

The team is not sure if the injury will keep Cooper out for the season. The injury occurred in the third quarter.

Cooper, drafted seventh overall in this year's draft, started at left guard for the Cardinals on Saturday. He was the first offensive lineman Arizona had selected in the first three rounds since the team took Levi Brown fifth overall in 2007.

"He has a unique skill set, maybe one of the more athletic offensive linemen I've [scouted] in the 15 years I've been in the business," Cardinals general manager Steve Keim said on draft day. "He has tremendous feet, bend, athleticism, space skills, and the ability to pull and play on the perimeter."

Under new coach Bruce Arians, the Cardinals are looking to jump start an offense that ranked last in the league in total offense in 2012-13. To that end, Arizona drafted Cooper and signed quarterback Carson Palmer as well as running back Rashard Mendenhall in the offseason.

ESPN.com's Mike Sando contributed to this report.