So far, everything seems to be going right for LSU.

Les Miles not only saved his job as head coach last season, but managed to turn a hot seat into a hot program by making a recruiting day splash (nation’s composite No. 3 recruiting class). Then he picked up a huge hire in defensive coordinator Dave Aranda.

Meanwhile, the Tigers retained more senior talent than normal — proven stars like linebacker Kendell Beckwith, receiver Travin Dural, defensive tackle Christian LaCouture and center Ethan Pocic chose to stay in school — and spring, by all accounts, went well for the Tigers’ Achilles heel, the often anemic passing game.

ESPN’s Mark Schlabach had the Tigers as the nation’s No. 6 team after National Signing Day, a sign that LSU is ready to return to being a national title contender — at least until the Alabama game.

But all that makes assumptions. Players will progress. Talent will work itself out.

Or will it?

There are things that can go wrong that can make the plan go sideways.

Here’s what LSU can’t have happen before the season opener:

1. The puzzle pieces don’t fit the defense

Aranda is making a bold move shifting LSU from a 4-3 scheme to a 3-4 on defense, but former recruiting coordinator Frank Wilson (now Texas-San Antonio) and company spent years focusing on recruits who fit into the old scheme, particularly up front.

Can the mostly 4-3 personnel adjust to the new system or are they the wrong fit?

Nose tackle Davon Godchaux was thought of as a 4-3 defensive end coming out of high school and progressed to a 4-3 defensive tackle. But a nose tackle?

He’s not the only question mark.

Christian LaCouture was recruited as a 4-3 defensive tackle, not as a 3-4 end. Tashawn Bower was brought in as a defensive end, not an outside linebacker. Meanwhile, LSU allowed Alabama to come into Louisiana and grab O.J. Smith, a natural nose guard, with little resistance back in 2014, an example of where LSU passed on tailor-made 3-4 players because it wasn’t a 3-4 program.

Certainly, as the Tigers covet players who are natural to the scheme, this will change over time. But for now, do the players fit? Godchaux seems like a gamble at noseguard given his smallish stature under 300 pounds. Bower is bulky for an outside linebacker.

There are players who seem like natural fits. Arden Key, for one, was small for a defensive end, sort of like Barkevious Mingo was when he played for the Tigers. It would seem playing standing up in a 3-4 might be a more natural fit for Key. Time will tell.

Miles is a coach who likes to run the ball and play good defense. That should continue to be his preferred formula with Leonard Fournette at running back. If the Tigers can’t adjust to the new scheme and start giving up points in bunches, that will spell big trouble for this team.

2. Brandon Harris and the passing game don’t improve

This is LSU’s perennial problem, isn’t it? So why isn’t it the No. 1 thing that can derail this team?

It’s simple. The Tigers have done pretty well without an explosive passing game in the past with the defense-and-ball-control formula. If the defensive part of the that equation is compromised, then even an improved passing game probably won’t save the season.

That said, LSU probably can’t win the league and advance to the playoffs if it’s 12th in the SEC in passing yards, like it was last season. Harris has to improve in every way and touted receivers like Malachi Dupre, Travin Dural and Tyron Johnson have to live up to their billing.

For this team to win big, defenses have to pay for stacking the line to stop Leonard Fournette. Last season, that didn’t happen enough.

3. Leonard Fournette isn’t locked in

Certainly, you’ve seen it before. A player becomes a star, gets caught up in his own hype and ends up a little out of shape, or just not as locked in.

LSU can withstand a slump from Fournette to an extent because its stable of backs is so talented. It’s not hard to imagine backup Derrius Guice emerging as an all-SEC talent in his own right.

But it is hard to imagine a blueprint to the national championship for the Tigers that does not involve Fournette hitting on all cylinders. The Tigers would still be good at the position, but they probably need greatness from Fournette to get over that Alabama hump.

4. The offensive line loses its edge

One didn’t sense a ton of confidence with the offensive tackle position, where the Tigers lost both starters from last season, at the end of spring.

Maea Teuhema struggled at times at left tackle and the possibility exists that center Ethan Pocic could move to that spot. Meanwhile, Toby Weathersby looked good at right tackle, but after he suffered an injury, K.J. Malone saw significant time there.

If LSU ends up having to shuffle pieces around in August and can’t find the right chemistry, will the offensive line be dominant enough to open the holes Leonard Fournette needs to have the kind of year LSU needs him to have? And if they don’t protect Harris early in the year, it would make it hard for a struggling quarterback to find his confidence.

5. The 3 a.m. phone call

Les Miles was asked about avoiding the “3 a.m. phone call” during the press conference following the spring game. That, of course, implies that a player has gotten in trouble.

Miles joked that “if the phone rings at 3 a.m., I’m not answering it.”

He’s had to answer his share over the years. Remember the bar fight that involved quarterback Jordan Jefferson? Or the dismissal of Tyrann Mathieu? The Tigers, like a lot of SEC teams, have had their share of offseason problems.

The roster looks like a contender right now. What it can’t afford is the subtraction of key players for off-the-field transgressions.