Matt Brown, Ben Ericksen, Evan Frierson and Mike Zimmer each signed free-agent deals with NFL squads.
Walker, Underwood and Ericksen all had standout seasons in 2012.
The Redbird duo has been honored by several organizations following the 2012 season.
The All-America honors are the second this week for both Underwood and Ericksen.
Underwood is ISU's first player to be named a first-team selection by TSN since 2007.
2012 Redbird Football Spring Camp (April 5)
2012: Third-Team All-America selection by The Sports Network and the Associated Press ... selected to the College Sporting News 2012 Fabulous Fifty FCS All-America Team ... College Sports Journal Football Championship Subdivision (FCS) All-America Team pick ... All-MVFC First-Team member ... finished the season ranked No. 4 in the country in interceptions per game and led the conference with seven interceptions ... ranked sixth on the team with 67 tackles, one sack and 3.5 tackles-for-loss ... named the national and MVFC Defensive Player of the Week, after intercepting two passes and finishing with four tackles in a win at Eastern Michigan ... also intercepted a pair of passes against Missouri State ... recorded a career-best 12 tackles in the second-round playoff victory at Appalachian State.
2011: Started all 11 games at free safety and returned kickoffs ... averaged 17.1 yards on 12 kickoff return, with a season-long 33-yard return at Eastern Illinois ... also had a 20-yard return at Youngstown State and a 22-yard return at Southern Illinois (10/29) ... tied with Eric Brunner for most fumbles recovered with three ... recorded 27 tackles, including two tackles-for-loss, one forced fumble and three pass breakups ... had a season-high four tackles against Western Illinois.
2010: Played in eight games, with one start at wide receiver ... missed three games due to a leg injury ... returned 34 kickoffs for 917 yards for an average of 27 yards per return ... the 27 yards per return set a new ISU single-season record ... recorded 26 kick returns on the season of 20 yards or more and eight of 30 yards or more ... returned the season-opening kickoff 85 yards for a touchdown against Central Missouri ... returned a kickoff 89 yards that set up a touchdown on the very next play in a win over Missouri State ... also caught eight passes for 82 yards on the season.