The Broncos will be without defensive end Courtney Brown for the entire exhibition season after he underwent arthroscopic surgery on his troublesome left knee. Recovery is expected to take three to four weeks. Coach Mike Shanahan said Thursday he expects Brown to be back in the lineup for the Broncos' regular season opener at St. Louis. "We have four weeks, and I feel pretty good that he should be able to come back if there are no setbacks," Shanahan said. "We will keep our fingers crossed."