Up front, there are answers. Deep behind the line of scrimmage, there are unknowns.

Last year, Missouri ranked third in the SEC by allowing 169.3 yards passing per game. There’s potential for the Tigers’ pass defense to be strong again. But some must assert themselves to help compensate for the losses of linebacker Kentrell Brothers, safety Ian Simon and cornerback Kenya Dennis.

Here’s how the Tigers’ passing defense performed in some key categories in 2015:

Passing yards allowed per game (SEC rank): 169.3 (3rd)
Most yards allowed: 303, Mississippi State
Passing TDs allowed: 10 (tied, fewest)
300-yard passers allowed: 1 (Dak Prescott)

The defensive line, highlighted by ends Charles Harris (below) and Walter Brady, likely will make life difficult for quarterbacks this year. A strong pass rush will be necessary for the Tigers to limit offenses through the air as the secondary moves on without Simon and Dennis, two key presences last year. The good news is that talent at end and tackle is in ample supply.

Sep 19, 2015; Columbia, MO, USA; Connecticut Huskies quarterback Bryant Shirreffs (4) throws a pass as Missouri Tigers defensive end Charles Harris (91) defends during the second half at Faurot Field. Missouri won 9-6. Mandatory Credit: Denny Medley-USA TODAY Sports

Credit: Denny Medley-USA TODAY Sports

Meanwhile, Missouri will need big seasons from safety Anthony Sherrils and cornerback Aarion Penton. If others create an impact in the secondary, offenses could find trying to throw against the Tigers tough once more.

PASS RUSH

Expect some flexibility here, but Missouri should operate from a 4-3 base with three-man fronts in some situations. Harris and Brady highlight the pass-rush discussion – more on them later – but defensive tackle Terry Beckner Jr. returns after totaling three sacks last season and linebacker Donavin Newsom will be back after producing 2.5.

Prepare to see Rickey Hatley, Josh Augusta, Josh Moore and possibly Harold Brantley, if he can add weight and catch up in the classroom, to make their presence felt at defensive tackle. The ability to operate out of a three-man front gives the Tigers the chance to produce different looks, but the talent is best suited for a four-man front. It wouldn’t surprise to see coach Barry Odom play to his strengths after receiving an up-close look at what worked well last year as Missouri’s defensive coordinator.

In addition to Newsom, Michael Scherer and Joey Burkett will be favorites to start at linebacker. Scherer (below), who was second on the team with 93 tackles last year, will try to help fill the void left by the loss of Brothers, who had a team-high 152 tackles in 2015. Newsom was fourth with 63.

Nov 21, 2015; Columbia, MO, USA; Tennessee Volunteers running back Alvin Kamara (6) is tackled by Missouri Tigers linebacker Michael Scherer (30) during the first half at Faurot Field. Mandatory Credit: Denny Medley-USA TODAY Sports

Credit: Denny Medley-USA TODAY Sports

SACK ARTIST

It could be double the trouble for quarterbacks this season. Harris and Brady (below) led Missouri with seven sacks each last year, and they will be back with the potential to wreak havoc again.

Nov 5, 2015; Columbia, MO, USA; Missouri Tigers linebacker Clarence Green (40) and defensive lineman Walter Brady (56) bring down Mississippi State Bulldogs quarterback Dak Prescott (15) during the second half at Faurot Field. Mississippi State defeated Missouri 31-13. Mandatory Credit: Jasen Vinlove-USA TODAY Sports

Credit: Jasen Vinlove-USA TODAY Sports

The presence of both players is a large reason the Tigers’ line will be fascinating to watch. Both are explosive on the end, and after the damage they caused in 2015, they represent one of the most tantalizing one-two defensive punches in the SEC.

So what’s next? Push for more.

With both a year older and more experienced, Harris and Brady should aim to top what they accomplished last year. If they do, that will be bad, bad news for opposing quarterbacks. They’re powerful, athletic and wicked to try to contain when they find room to work.

There weren’t many duos in the SEC with more sacks than the 14 from Harris and Brady last year. Only Alabama’s Jonathan Allen and Tim Williams (22.5), Texas A&M’s Myles Garrett and Daeshon Hall (19.5) plus Tennessee’s Derek Barnett and Jalen Reeves-Maybin (16) were better.

A large reason for the optimism surrounding Missouri’s defense is the line’s potential. Harris and Brady are big parts of the conversation.

BALL IN THE AIR

The Tigers begin with questions in the secondary. Missouri must replace Simon and Dennis, both significant contributors last season, and it’s unclear how the Tigers will fare without them.

Sherrils will be a staple at safety after totaling 64 tackles and six pass breakups last year. Look for Penton (below), who had 59 tackles and a team-high eight pass breakups in 2015, to be a strong presence at cornerback.

Sep 5, 2015; Columbia, MO, USA; Missouri Tigers cornerback Aarion Penton (11) celebrates after a tackle during the second half against the Southeast Missouri State Redhawks at Faurot Field. Missouri won 34-3. Mandatory Credit: Denny Medley-USA TODAY Sports

Credit: Denny Medley-USA TODAY Sports

But beyond those two, there’s much to be learned. Cornerback T.J. Warren, a redshirt freshman, had a standout spring and is in the running for a starting job. He’ll compete with rising junior Anthony Hines, who saw time in the rotation last year.

Meanwhile, Cam Hilton switched from slot receiver to safety in the offseason to help address the thin depth at the position. Thomas Wilson had the top job over Hilton exiting spring practices, but more remains to be discovered there.

Penton and Sherrils should be standouts again. But clearly there are unknowns elsewhere, particularly at safety. It will be interesting to see if the Tigers can grow into another formidable pass defense.

PICKOFF ARTIST

Consider this category “to be determined.” Simon and Brothers are gone after they led the team with two interceptions each last year.

Perhaps Penton, who had one interception last season and a career-high three in 2014, will step forward as the top pickoff threat as the season progresses. But there’s room for someone to assert himself here.

GREATEST CONCERN

It has to be the secondary. After Missouri’s defensive backs became a clear strength last year, it remains to be seen how the Tigers will replace Simon and Dennis.

Expect solid play from Sherrils and Penton, but Missouri will need others to take a step forward. It will be worth watching the secondary’s development all season.

ONE STAT THAT MUST CHANGE IN 2016 

There’s not one glaring area, given how strong the Tigers were against the pass last season. However, there’s room for improvement when it comes to opponent completion percentage.

Missouri allowed quarterbacks to complete 61.9 percent of their passes last year, which ranked 12th in the SEC. Of course, opponents threw 354 times against the Tigers, which was the fourth-fewest total in the conference. Still, Missouri had 53 passes defended last season, which ranked 12th in the conference and Tigers defenders produced 44 pass breakups, which ranked 11th. It would help to see those numbers rise.

BETTER/WORSE IN 2016

It’s hard not to think there might be some drop off. Missouri must replace two key figures in the secondary, and it’s uncertain how those stepping in will perform.

The pass rush should be stellar, and the Tigers expect big things from Sherrils and Penton. Missouri left such a high bar for itself that it’s possible the Tigers will remain strong against the pass but be “worse” in this category in the fall.

Until more answers are learned about the secondary’s personality, it’s fair to approach the pass defense with curiosity to begin the season. More will be discovered in time.