The Lions practiced in front of season ticket holders Sunday, and the defense responded to the boisterous crowd with a solid effort. Like pitchers in baseball’s spring training, NFL offenses often dominate early camp workouts. Defenses – like hitters – catch up eventually, however, and Detroit’s unit has improved with each passing day. Here are some defensive highlights from Day 3:

CB Jacob Lacey shines in first team role: The hotly-contested competition to start opposite Chris Houston at cornerback took a turn Sunday when free-agent signing Jacob Lacey replaced Alphonso Smith in the first-team role. Jacob Lacey took advantage of the change in the depth chart, making an interception in coverage drills in addition to several pass breakups. After an average performance during Detroit’s first two open practices, Lacey’s effort Sunday rekindled the opinion that he can be a legitimate challenger for a starting CB spot.

LB Whitehead impresses vets: Rookie Tahir Whitehead, who was a virtual unknown to most Lions’ fans when Detroit selected him in the fifth round of the 2012 draft, has been one of the most consistent rookie performers early in camp. His ball pursuit in run situations has been impressive enough to earn him second-team reps, although he’s often the odd man out in nickel package situations. LB Stephen Tulloch, whose experience in Jim Schwartz’ system can serve as a good gauge for evaluating players’ effectiveness, says he’s impressed by Whitehead’s play. “He’s explosive, smart, and he doesn’t make the same mistakes [twice],” Tulloch said. “Whenever you see a rookie that corrects his mistakes, it’s a positive. That’s a guy you can trust on the field.”

D-line finds extra gear in workout: While it’s often difficult to gauge the progress of the offensive and defensive lines until teams practice in full pads, Detroit’s D-line stepped up its intensity in Sunday’s workout. DE Kyle Vanden Bosch stripped WR Nate Burleson to force his first fumble of camp. Despite concerns over Vanden Bosch’s age and health, he remains one of the hardest workers on the defensive side of the ball. That work ethic hasn’t been lost on DEs Willie Young and Lawrence Jackson, who are taking advantage of the first-team reps they’re splitting while Cliff Avril continues his holdout. Both players are moving well off the line, and surely would have sacks to their credit if contact with the quarterback were allowed. The starting DE job opposite Vanden Bosh still belongs to Avril when he returns, but Young and Jackson’s efforts indicate the Lions should enter the season with outstanding D-line depth.

Follow Lions reporter John Kreger on Twitter: @CBSSportsNFLDET and @johnkreger.