Eight NFL defenses that have improved the most

Josh Norman's emergence has given Carolina's D a boost. Grant Halverson/Getty Images

Which defenses have made the most improvements since last season? This wasn't an easy list to compile, as several of the teams listed below are experiencing rough times after strong starts.

This list wasn't compiled based just on stats, but also how teams look on tape. Denver's defense is improved, as it now stands as the top unit in football. But it was also exceptional last season, so it didn't make the cut.

Below are eight teams, in alphabetical order, that have improved the most on defense from last season.

Carolina Panthers

Although the Panthers weren't terrible on defense last season, they now boast what could be the league's second-best defense behind Denver's. Luke Kuechly and Thomas Davis remain stalwarts at linebacker. This season, Kawann Short (DT) and Josh Norman (CB) have joined them as elite players. The Panthers were not all that difficult to run on last season, which isn't the case anymore.

This group also excels at creating turnovers, which can stem from its great pass rush. Just the Broncos, Rams and Patriots have more sacks than Carolina. On a yards-per-pass basis, this is the best defense in football. And when DE Charles Johnson returns from injury, the Panthers' pass rush will get a needed boost.