Welcome to the start of what may be the most challenging offseason of coach Les Miles’ nine-year tenure at LSU.

A defense gutted by the loss of seven starters — a record 11 players bolted early for the NFL draft — and a shift in gears to a new offensive coordinator with a mandate to make the unit more productive are the issues that shadow the Tigers when they begin spring practice Thursday.

They begin working with an eye toward an exceptionally daunting schedule, which begins in a little less than six months with the Cowboys Classic against TCU in Arlington, Texas.

The Tigers are coming off an almost-but-not-quite 2012 season in which they went 10-3 and finished No. 12 in the USA Today coaches’ poll and No. 14 in the AP poll.

By almost any standard, the season was a solid one, but it was marked by three increasingly frustrating losses that had their roots in an offense that was unable to be productive at critical times.

The Tigers couldn’t manage to score a point in the second half of a 14-6 loss at Florida. Then LSU failed to convert critical first-down opportunities late in the Alabama game and the Chick-fil-A Bowl against Clemson, allowing both teams to escape with last-minute victories (21-17 by Alabama, 25-24 by Clemson) in games that LSU dominated for long stretches.

Immediately after the bowl game Miles vowed improvement on offense. To that end, he brought in former Baltimore Ravens offensive coordinator and close friend Cam Cameron.

To do that, though, Miles had to delicately navigate former offensive coordinator Greg Studrawa back to strictly being offensive line coach and shipped former quarterbacks coach Steve Kragthorpe off into an administrative role.

Cameron inherits an offense that actually averaged more yards than it did in 2011 — 374.2 to 355.1. But scoring slipped from 35.7 to 29.8 points per game, as did first downs (269 to 242), third-down conversions (45 percent to 40) and, most markedly, total touchdowns (65 to 46).

The good news for Cameron and his new charges is that the offense returns most of its major pieces. Running backs Spencer Ware and Michael Ford left early for the draft — as did, surprisingly, injured left tackle Chris Faulk — but senior quarterback Zach Mettenberger is back and surrounded by a host of skilled talent.

The Tigers return their top two rushers in sophomore Jeremy Hill and Kenny Hilliard — plus Alfred Blue, who began the season as the starter but suffered a knee injury in Week 3 against Idaho.

Blue is expected to practice this spring, LSU sports information director Michael Bonnette said, but only in a green jersey signifying no contact allowed.

The top four receivers are also back, led by the junior tandem of Jarvis Landry and Odell Beckham Jr.

Defense is the big issue. Gone are all four line starters, though tackles Anthony Johnson and Ego Ferguson were arguably as key as departed starters Bennie Logan and Josh Downs. Also gone early to the draft are middle linebacker Kevin Minter and his team-leading 130 tackles, cornerback Tharold Simon and free safety Eric Reid.

The Tigers also will be breaking in two new specialists in place-kicker James Hairston (he handled kickoffs last year) and punter Jamie Keehn. Keehn had punting chores in LSU’s opener and the bowl game, when Brad Wing was suspended.

Eight signees from LSU’s 2013 recruiting class will take part in spring practice: quarterbacks Hayden Rettig and Anthony Jennings; receivers Avery Peterson (formerly Johnson) and John Diarse; tight end Logan Stokes; offensive tackles Fehoko Fanaika and Ethan Pocic; and defensive end Christian LaCouture.

Since they are getting an early start to their college careers, Rettig and Jennings are expected to provide a challenge to sophomore Stephen Rivers for the role of Mettenberger’s backup and the inside track to be his successor for the 2014 season.

Rob Bolden, the quarterback who transferred from Penn State last season, is recovering from a knee injury he suffered during practice last season and will be limited, Bonnette said.

The Tigers wrap up spring practice with their spring game at 2 p.m. April 20 in Tiger Stadium. There will be no admission charge.