(Part 6 of a 14-part SEC football preview series)

Besides finding a successor for Johnny Manziel, the Texas A&M Aggies have multiple matters to address defensively.

Manziel, who became the first freshman to win the Heisman Trophy in 2012 and was a finalist behind another freshman, Jameis Winston, in 2013 is one of only five returning starters on offense. In all, the Aggies must replace three first-team All-SEC performers (Manziel, wide receiver Mike Evans and right tackle Jake Matthews) from an offense which led the SEC in scoring (44.2 points per game), total offense (538.4 yards per game) and passing (353.3 ypg).

Despite the prolific numbers, the Aggies (9-4, 4-4) were only able to produce a .500 record in conference play before finishing out the campaign with a 52-48 victory over Duke in the Chick-fil-A Bowl.

Third-year head coach Kevin Sumlin is counting on a veteran offensive line to help make the transition easier for the new quarterback.

Senior left tackle Cedric Ogbuehi, a potential first-round draft choice, is among four holdovers on the forward wall. Sophomore right tackle Germain Ifedi moves from right guard to right tackle while senior Jarvis Harrison and junior Mike Matthews return at left guard and center, respectively.

Senior Malcome Kennedy (60 receptions, 658 yards, 7 touchdowns), the team's second-leading receiver, is the lone returnee at the skill positions.

Sophomore Kenny Hill and freshman Kyle Allen are the leading candidates to step in at quarterback. Hill completed 16-of-22 passes for 183 yards and one touchdown in four games as Manziel's backup. Allen, the nation's top-ranked prep quarterback out of Scottsdale (Ariz.) Desert Mountain, enrolled in January.

Junior tailbacks Tra Carson (62 carries, 329 yards, 7 touchdowns), Trey Williams (58-407-6) and Brandon Williams (44-269-1) are capable replacements for Ben Malena. Trey Williams also returned 28 kickoffs for a 25.2-yard average.

While the offense ranked at or near the top of the SEC in virtually every category, the defense was alarmingly generous. Texas A&M ranked dead last in the 14-team circuit in points allowed (32.2), total defense (478.5 yards per game), rushing defense (222.3 ypg) and 12th in passing (253.5 ypg).

First-team All-SEC senior cornerback Deshazor Everett (73 tackles, 2 TFL, 2 interceptions) heads up the unit along with senior strong safety Howard Matthews (90 tackles, 2.5 tackles for loss, 3 interceptions), who was second on the team in tackles.

Among the other key returnees are junior corner De'Vante Harris (56 tackles, 2.5 TFL, 8 pass breakups), senior free safety and former East St. John standout Floyd Raven Sr. (38 tackles, 2 blocked kicks), junior defensive end and Brother Martin product Julien Obioha (38 tackles, 5 TFL, 1 sack) and junior defensive tackle Alonzo Williams (27 tackles, 2.5 TFL, 2.5 sacks).

Junior Drew Kaser was a first-team All-SEC punter after leading the conference with a school-record 47.4-yard average on 44 attempts with 17 punts of 50 yards or more.

Junior Josh Lambo, a former first-round pick by FC Dallas of Major League Soccer, converted 8-of-10 field goal tries including a career-long 45-yarder in the Chick-fil-A Bowl.