San Diego Chargers rookie linebacker Donald Butler was carted off the practice field today after suffering an ankle injury, Kevin Acee of the San Diego Union-Tribune reports.

Butler was being examined tonight.

San Diego traded up to the third-round to draft Butler, a 6-1, 245-pound inside linebacker from the University of Washington. A two-year starter who was sort of hidden until the 2009 season, Butler led the Huskies with 94 tackles as a senior.

After a good week at the Senior Bowl in Mobile, Butler showed off his strength at the Combine (35 reps on bench press) and athleticism (4.61-40, 35" vert.) during his pro day at UW, establishing himself as a legitimate mid-round prospect.

Because the University of Washington operates on the "quarters" system, Butler missed most of the team's OTA sessions. A prolonged training camp absence due an injury could limit his effectiveness during his rookie season. The Chargers view Butler as a starting inside linebacker down the road, but his primary contributions this season are likely to come on special teams.