The Detroit Lions surged in their first season under head coach Jim Caldwell, as the team finished 11-5 and made the playoffs as a widcard. The goal is to make it even further this year, as 27-year-old quarterback Matthew Stafford enters his seventh NFL season and presumably his prime. Although the Lions were dealt some early adversity, tough situations have helped them explore every corner of their roster this preseason.

With the regular season set to kick off on Thursday, here are the five most important things we learned from the Lions' preseason.

1. The Lions have options at running back

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Starting running back Joique Bell spent most of the summer on the physically unable to perform (PUP) list, but a pair of rookies stood out in his stead. Ameer Abdullah, a second-round pick in this year's draft, brings electricity to Detroit's offensive backfield; Zach Zenner, an undrafted FCS product, brings a bit of grit. And don't forget about third-year pro Theo Riddick, who's notably skilled as a pass-catcher.

2. No one player will be able to replace Ndamukong Suh

The Lions lost Suh in free agency this spring, and it didn't take long to realize that they can't rely on just one player to replace his impact on defense. Although they traded for All-Pro defensive tackle Haloti Ngata, the Lions are also counting on Caraun Reid, Tyrunn Walker and everyone else in the front seven to help fill the void created by Suh's departure this offseason. This will be one of the Lions' biggest challenges.

3. A strong secondary will lead the defense

Detroit had one of the league's best defenses last season, but the unit will be much different this year. Without Suh, the Lions' biggest defensive stars now reside in the secondary. Cornerback Rashean Mathis and safety James Ihedigbo are both seasoned veterans; Pro Bowl safety Glover Quin is in his prime and third-year cornerback Darius Slay may be on the verge of a breakout season.

4. The Lions are bringing Laken Tomlinson along gradually

The Lions spent the 28th-overall pick in this year's draft on Tomlinson, but they were in no rush to thrust him into the starting lineup. He started out splitting first-team reps with Manny Ramirez at left guard, which afforded him the flexibility to adjust to the NFL game at a comfortable pace. Tomlinson is expected to play a large role in Detroit's youth movement along the offensive line, so a premium has been placed on proper development.

5. The third pass-catcher remains a mystery

There's still no telling who's going to step up as a receiving threat behind the Lions' top two wideouts -- Calvin Johnson and Golden Tate. T.J. Jones, who scored 64-yard touchdown in the preseason finale, was the only wide receiver to cause as much as a ripple this summer. If Corey Fuller and Lance Moore aren't viable contributors, the Lions better hope either second-year pro Eric Ebron or recent trade acquisition Tim Wright turns out to be a game-changer at tight end.