Cornerback Bryon Fields will return to action this year after missing the entire 2015 season with ... Duke football 2016 position preview: Defensive backs With the 2016 season right around the corner, The Chronicle's football beat writers break down each of the nine major position groups: quarterbacks, running backs, receivers, offensive line, defensive line, defensive backs, linebackers, kicker/punter and punt/kickoff returners to prepare you for the regular season.Duke’s secondary was unable contain opposing passing attacks down the stretch last season. The Blue Devils surrendered over 330 yards passing in their last three games and finished the year ranked 12th in the ACC in passing defense. The struggles in the secondary were in part because the defensive line did not generate pressure on opposing quarterbacks, which forced the defensive backs to defend in coverage longer.But injuries and fatigue in the secondary also took a toll. Starting cornerback Bryon Fields missed the entire season recovering from a torn ACL in his right knee, forcing the Blue Devils to rely heavily on then-freshman Jeremy McDuffie.Although Duke will have to overcome the departure of first-team All-American safety Jeremy Cash, the return of Fields has boosted the secondary. The Blue Devils also hope that an offseason emphasis on strength and conditioning will help prevent them from tiring toward the end of the season.Key players lost: S Jeremy CashThe Blue Devils’ best defensive player throughout the last three years, Duke relied on Cash to make plays both at the line of scrimmage against the run and in the defensive backfield. Defensive coordinator Jim Knowles has said that Cash—who led the Blue Devils with 18 tackles for loss in 2015—often made up for poor play calls and teammates' mistakes.Duke will turn to redshirt senior Corbin McCarthy to replace Cash. Although he was Cash’s backup since his redshirt freshman year, McCarthy has played in every game in the last three seasons with six career starts. As one of the Blue Devils’ strongest and fastest defensive players, the Norco, Calif., native's versatility should make him a good fit at the strike safety position.Cutcliffe on the secondary:Defensively, there’s no question that secondary shows up. They were outstanding on third downs. Outstanding.They forced some turnovers. They played with a little more confidence. That secondary is very confident and experienced. Bryon Fields has really gotten off to a really good start.Projected starters:Breon Borders and Fields will start at cornerback, and DeVon Edwards, Deondre Singleton and McCarthy will start at the rover, bandit and strike safety positions, respectively. McDuffie is expected to back up Borders and Fields.Borders, Edwards and Singleton each started all 13 games last season and carry some chemistry in the secondary into their final season at Duke. Borders led the Blue Devils with three interceptions in 2015 and Edwards spent much of the offseason preparing to be the team's other cornerback, but shifted back to safety in fall camp when Fields was fully recovered from his injury.Dark horse: CB Mark Gilbert Although Gilbert likely will not see the field early on, the true freshman's playing time will increase if Fields, Borders or McDuffie suffers an injury. The 6-foot-1 Fayetteville, N.C., native—who drew college offers from Michigan, South Carolina, Louisville and North Carolina—can use his combination of size and speed to stay in front of opposing wide receivers and go after jump-balls aggressively.Be sure to stay with the Blue Zone for our continuing 2015 position preview series. Check in tomorrow to see how Duke is going to replace All-ACC punter Will Monday and All-ACC kicker Ross Martin.Ben Feder and Hank Tucker contributed reporting.