The Detroit Lions closed out their 2025 preseason with plenty of positives, but also some glaring concerns as they turn their attention to Week 1 of the regular season.

From winners of position battles emerging to depth chart worries, here are five key lessons the Lions learned over the past month of exhibition play.

Hendon Hooker isn’t ready for primetime

The Lions entered camp hopeful that Hooker could push for the backup quarterback role, but the former third-round pick didn’t deliver.

Hooker struggled to generate meaningful drives and consistently left the offense sputtering.

Even when he strung together a positive play, it was often undone by penalties or his own mistakes.

That lack of rhythm and consistency cost him the chance to cement a roster spot.

While his long-term potential remains uncertain, the 2025 preseason made it clear Hooker isn’t ready to be relied upon behind Detroit starting signal-caller Jared Goff.

Isaac TeSlaa validated the hype

If Hooker was the biggest disappointment, rookie wide receiver Isaac TeSlaa was easily the breakout star of the preseason.

The third-round pick showcased toughness, reliable hands and a nose for the end zone throughout camp and the preseason slate. His 33-yard touchdown grab against the Texans marked his third straight game with a score, further cementing his role in the offense.

TeSlaa’s performance throughout camp not only earned him a spot on the 53-man roster, but also hinted he could contribute immediately as a red-zone weapon and possession target.

For a Lions offense that thrives on depth, his emergence is a major boost.

Terrion Arnold looks ready for a bigger role

After an uneven rookie season, the second-year cornerback flashed noticeable improvement.

His coverage looked sharper, his instincts more refined and his physicality at the line gave Detroit’s defense an edge in joint practices against top-tier opponents.

With DJ Reed providing veteran leadership, Arnold’s growth is crucial for a secondary that has been seeking stability.

If he can stay healthy, Arnold appears poised to step into a key role, potentially becoming the shutdown corner the Lions envisioned when they made him their first-round selection a year ago.

Starters are in regular-season form

Lions head coach Dan Campbell expressed confidence that Detroit’s first-stringers are exactly where they need to be heading into Week 1.

The starting offense looked crisp and balanced, while the defense showcased a solid degree of physicality and toughness. Facing quality opponents in joint practices, like Miami and Houston, also provided valuable tests for both sides of the ball.

“I love where our team’s at,” Campbell said after the Lions’ preseason finale against Houston. “We just finished basically six weeks, five weeks of true work on the grass and we’ve gotten better and better every week on both sides of the ball. I feel like we’ve really progressed.

“We’ve gotten two different looks from other teams, too, Miami and Houston this week. And I just think we’ve gotten a variety of work, I think we’ve tested each other, I think we’ve grown from it and I think we’re going to be ready to go. I’m fired up right now, so we’re going to be good.”

The Lions’ starters appear primed for a strong start to the regular season.

Depth remains a concern at multiple areas

Despite the positives, Detroit’s roster weaknesses were exposed, particularly at offensive tackle and in the secondary.

For starters, the Lions are dangerously thin behind starters Taylor Decker and Penei Sewell. And if either of them goes down for an extended period of time, career backups Dan Skipper and Jamarco Jones, along with unproven players like Giovanni Manu, will be thrust into critical roles.

The situation is perhaps even more bleak in the defensive backfield.

With Ennis Rakestraw lost for the year and Arnold battling the injury bug earlier this preseason, the Lions may be one more ailment away from serious trouble.

The safety group also lacks depth, forcing Avonte Maddox and undrafted rookie Ian Kennelly likely into bigger roles than the team originally expected.