The defending champion Baltimore Ravens have several key starters to replace from last season, including inside linebacker Ray Lewis, and that's why they traded up in the second round to draft Arthur Brown out of Kansas State. Brown was one of the highest-rated inside linebackers in the draft and is expected to start as a rookie, but he's now estimated to be sidelined for 4-6 weeks following sports hernia surgery.
The team also lost defensive players such as Paul Kruger, Dannell Ellerbe, and Ed Reed to free agency, but Brown was the only linebacker drafted by the Ravens. They did sign outside linebacker Elvis Dumervil, but Brown is expected to play an integral role to the team in 2013.
The timetable should still allow Brown to return for training camp and be ready for exhibition season, though it is never ideal to have players fall behind during their first season. Brown was the Big 12 Defensive Player of the Year in 2012. If he's going to win NFL Defensive Rookie of the Year, he'll just have to do some catching up in July.