Texas A&M can spend all week debating whether Marcel Reed should remain its starting quarterback. But if Mike Elko wants to identify another major reason his Aggies are 1-4 in SEC play, he might want to start with the defense.

Because Saturday afternoon in Tuscaloosa, Texas A&M's defense had an opportunity to win a football game.

MORE: Marcel Reed's Turnovers Doom Texas A&M In 31-20 Loss To Alabama

Instead, it folded.

The Aggies carried a 20-17 lead into the fourth quarter against No. 13 Alabama before surrendering two touchdowns in a 31-20 loss that exposed some troubling problems with a unit that's supposed to be the foundation of Elko's program.

Alabama quarterback Keelon Russell threw for 311 yards and three touchdowns, completing 19 of 30 passes while repeatedly finding openings in the Aggies' secondary.

His favorite target, Rico Scott, torched Texas A&M for six receptions and 156 yards.

That's 26 yards per catch.

And for a defensive-minded head coach, those numbers should be unacceptable.

The Aggies actually did an outstanding job limiting Alabama's rushing attack, holding the Crimson Tide to just 68 yards on the ground.

But that accomplishment meant little when Russell could consistently attack the secondary.

And when the game reached its defining moments, Texas A&M couldn't deliver the stops necessary to win.

The turning point came after Reed mishandled a fourth-down snap late in the third quarter, giving Alabama possession near midfield.

The Aggies needed their defense to respond.

Instead, Russell moved the Crimson Tide 45 yards in just four plays, connecting with Marshall Pritchett for a five-yard touchdown early in the fourth quarter.

Alabama led 24-20.

Texas A&M still had time to respond, but another empty offensive possession and a short punt put the defense back in a difficult position.

Once again, the Aggies couldn't hold.

Russell directed a five-play, 55-yard touchdown drive, finishing with an eight-yard scoring pass to Kaleb Edwards.

Just like that, Alabama had turned a three-point deficit into an 11-point lead.

Fourteen unanswered points.

Two touchdown drives.

And a Texas A&M defense that couldn't protect a fourth-quarter advantage.

Yes, Reed's interceptions and the offense's inability to score in the final period deserve plenty of criticism.

But championship-caliber defenses find ways to overcome offensive mistakes.

Elko built his reputation on defensive football, and the Aggies are supposed to be capable of winning games when their offense struggles.

Saturday demonstrated they're not consistently doing that.

Texas A&M falls to 4-4 overall, with its SEC championship ambitions effectively finished.

The quarterback debate will dominate the conversation, and understandably so.

MORE: No. 13 Alabama Missing Key Pieces, Outnumber Texas A&M on Final Injury Report

But Elko also needs to take a hard look at his defensive approach, secondary execution and ability to adjust when opponents attack his weaknesses.

Because if the Aggies can't protect a fourth-quarter lead against a quality SEC opponent, changing quarterbacks won't solve everything that's wrong with this football team.

Source: Yahoo Sports