SDS continues our series looking in-depth at teams and their biggest subplots heading into 2015. Next up: The LSU Tigers.

1. Improvement at quarterback

Without this essential ingredient, cooking up the kind of season LSU fans expect and demand will be a near impossibility. In 2014, the Tigers ranked last in the SEC in passing yards per game and completion percentage. The fact that they entered November with a 7-2 record is a testament to the strengths elsewhere on the team.

Of course, passing game struggles aren’t 100 percent the fault of the quarterbacks. LSU’s very young receiving corps was inconsistent in both getting open and holding on to catchable passes last season, but there’s plenty of talent at the position, and we should see more evidence of that this season.

The same is believed to be the case at quarterback, but there’s less confidence in that conviction. However, now that Brandon Harris appears to be establishing himself as the top option, optimism is on the rise again in Baton Rouge.

Harris reportedly received a “significant” edge in snaps with the offensive starters in the team’s most recent scrimmage on Saturday and completed 12 of 17 passes.

2. Who steps in while Jalen Mills is out?

He says he’s planning to be back by the time the Tigers take on Auburn in Week 3, but Mills, a veteran leader in the secondary, is expected to miss at least the first two games of the season and Les Miles offered no timetable for his return after Saturday’s scrimmage. Even meeting the most optimistic time frame, Mills appears sure to miss the trip to Mississippi State, which knocked off the Tigers last year in Baton Rouge.

Mills’ absence leaves a few question marks. A versatile three-year starter, Mills starts at safety in the base defense, but also lines up over the slot receiver in nickel packages, meaning it might require a couple of Tigers to fill his shoes.

Given the team’s traditional success at the position, it’s doubtful any LSU fans are losing sleep, but any time you’re missing a player of Mills’ talent for any amount of time, it’s worth noting.

Look for Dwayne Thomas to chip in as the extra corner in nickel sets and Rickey Jefferson to hold down Mills’ spot at safety while he’s out.

3. Get a pass rush

It’s mildly amazing that LSU had the success it had against the pass last season. The Tigers ranked first in the SEC passing yards allowed, passing touchdowns allowed, completion percentage allowed, and pass defense efficiency.

All that with only the whisper of a pass rush.

LSU finished with 19 sacks in 2014, second to last in the conference. It was the first time since 2000 that LSU finished the season with less than 20 sacks.

If the Tigers are to improve on that figure this year, it’ll have to be with new personnel. Both of last year’s starting defensive ends are gone, but Miles seems confident in their replacements, led by Tashawn Bower and Lewis Neal. True freshman Arden Key could also see the field early and provide a lift off the edge in passing situations.

And then there’s the matter of a scheme adjustment to consider. Kevin Steele is taking over for John Chavis as defensive coordinator and brings with him a shift in philosophies. Perhaps just as importantly, Ed Orgeron is now in charge of the defensive line at LSU, and has been heavily focused on generating sacks this offseason.

If successful, a pass rush more akin to what LSU is accustomed to should have a cascading effect throughout the defense. And if the pass defense is as good as it was last year, there’s a very high ceiling for the Tigers this season.

Speaking of which …

4. Every four years?

LSU is due for a title. Since 2003, the Tigers have claimed an SEC championship and reached the national championship game every four years, most recently in 2011.

Of course, big things were expected from the 2007 and 2011 teams. LSU opened 2007 at No. 2 in the AP poll after a dominant win over Notre Dame in the Sugar Bowl the previous season. And in 2011, the Tigers opened at No. 4 and immediately proved their legitimacy with a season-opening win over No. 3 Oregon.

Less will be expected out of this year’s team until it proves it has the quarterback riddle figured out.

But if you think back to August of 2003, LSU was in a similar predicament: going 8-5 the previous season while losing three of its last four, returning a pair of quarterbacks who split time the previous year, both failing to complete 50 percent of their passes.

But early in 2003, Matt Mauck took over the starting role at quarterback, and a defense that was expected to be pretty nasty developed into one of the most dominant college football has seen in recent years.

There are plenty of differences between that team and this one, but if LSU finds a quarterback that matches Mauck’s sturdy reliability, there’s reason to believe the rest could fall into place.