Minnesota Vikings quarterback Brett Favre, adhering to a timetable that would allow him to report to training camp, underwent arthroscopic surgery on his injured left ankle Friday morning by noted orthopedic specialist Dr. James Andrews, several sources told ESPN NFL Insider Chris Mortensen.

Favre's surgery occurred at the Andrews Institute in Gulf Breeze, FL., where Favre and his agent Bus Cook were spotted by a handful of people. Dr. Andrews cleaned up scar tissue and other elements of the joint to allow Favre a better range of motion, sources said. A source close to Favre said he would likely need four-to-six weeks of rehabilitation before beginning a running program that would put him on schedule to report to training camp "either at the beginning of camp or shortly thereafter." Favre had said he would need the surgery if he were going to play in 2010. He was unavailable for comment.