ALLEN PARK, Mich. -- The Detroit Lions accomplished everything they needed offensively this offseason.

Wide receiver Calvin Johnson looks healthy, quarterback Matthew Stafford improved his footwork, running back Reggie Bush appears fast and new receiving weapons Golden Tate and rookie Eric Ebron look like great fits at wide receiver and tight end.

On defense and special teams, though, questions remain, and those two units will likely determine the Lions' ceiling in 2014. Penalties could also remain an issue as the Lions had 25 combined in the final two preseason games.

"We have a ways to go. We really do," coach Jim Caldwell said Thursday after the Lions beat the Bills, 23-0. "We've got work to do, and we'll look forward to ... getting them in the right frame of mind."

Defensively the Lions actually have more potential problems entering the season than expected.

Tackle Nick Fairley was demoted during the preseason, and while C.J. Mosley is a solid player, he doesn't have the upside of the 2011 first-round pick. The Lions also drafted Kyle Van Noy in the second round hoping he could be a Day 1 starter at strong-side linebacker, but with him undergoing core muscle surgery Thursday, the Lions will rely on either Ashlee Palmer or Tahir Whitehead, who didn't play a defensive snap his first two seasons.

Then, of course, there's the secondary. The Lions are confident in second-year cornerback Darius Slay, veteran Rashean Mathis played well last year and Bill Bentley is a solid nickel option. But none proved to be consistent, lock-down defenders, and the cupboard is bare behind them. Plus, strong safety James Ihedigbo has been dealing with an unknown ailment.

Rookie kicker Nate Freese, a seventh-round pick, won his competition with Giorgio Tavecchio after showing consistent improvement over the summer. In the preseason finale, he made all three field-goal attempts, including two from 53 yards, but Freese will have to prove himself consistently under the pressure of the regular season.

Looking ahead to the Week 1 opponent, the New York Giants, the Lions should be optimistic they can start the season well. The crowd at Ford Field will be raucous for the "Monday Night Football" game, though the Lions lost their only Monday night game last season.

Quarterback Eli Manning seems still to be adjusting to the new playbook under offensive coordinator Ben McAdoo and, with his interception issues and first-round receiver Odell Beckham Jr. hampered by a hamstring injury, the Giants' passing attack looks like one that could provide a confidence boost for the Lions' weak secondary.

Defensively, the Giants have some playmakers, and their pass rush should be a good test for a Lions offensive line that is trying to prove it is as good as its performance last year when the team ranked second in the NFL with only 23 sacks allowed.

The Giants also still have a suspect secondary that Johnson, Tate and Ebron can exploit as long as Stafford makes good decisions, something the coaching staff has preached all offseason.

Even though the matchup appears to favor the Lions, the Giants won at Ford Field in Week 16 last year, 23-20, in overtime to eliminate the Lions from playoff contention. Stafford threw two interceptions, Bush lost a fumble and the Giants offense moved enough despite receiver Victor Cruz missing the game.

There is always a chance last year's game will provide more motivation for the Lions, who need to start the season with a win as they play 2013 division winners in their next two games at Carolina and versus Green Bay.

NOTES: Second round rookie outside LB Kyle Van Noy underwent core muscle surgery Thursday to fix an injury that created back and abdominal problems this offseason. Van Noy will miss the start of the regular season and is a candidate for the team's short-term injured reserve spot. ... Safety DeJon Gomes was waived with an injury settlement Friday, less than a week after he was placed on injured reserve. ... Starting SS James Ihedigbo did not make the trip to Buffalo for Thursday's exhibition finale in order to receive treatment back in Detroit. ... S Don Carey also stayed home for the preseason game in Buffalo and has been dealing with a hamstring injury he suffered last week against Jacksonville. Depending on his health, his roster spot is in danger with the emergence of safeties Isa Abdul-Quddus and Jerome Couplin, an undrafted rookie. ... DT Ndamukong Suh was not fined for his roughing-the-passer penalty on Jaguars QB Chad Henne last week.