ALLEN PARK -- The Detroit Lions coaching staff and front office continue to point to turnover differential as a key difference between the team's 2011 playoff campaign and its 4-12 disaster in 2012.

It's a fair point to highlight. The Lions went from fourth in the NFL last season (plus-11) to 30th in 2012 (minus-16). That's a nearly impossible difference to overcome.

After reviewing the team's performance with his staff, Lions general manager Martin Mayhew came to the conclusion that the only defensive starter who showed marked improvement was defensive tackle Ndamukong Suh. The others, whether it was because of age, injury, or talent, either plateaued or regressed.

"If you want to have a better defense, you have to have better individual performances, and we didn't have that this year," Mayhew said.

One area Mayhew feels he needs to improve the roster this offseason is the addition of play-makers -- the types of players who can consistently generate turnovers and make key stops -- especially in the back end.

"We have a lot of guys, who are good guys, that line up right, they know what their job is, but they don't impact the game," Mayhew said. "We need interceptors, guys that can sack the quarterback, we need guys that cause fumbles, that make plays on third down. Those are the kinds of guys that can change the game for us."

Mayhew referenced former Lions cornerback Dre Bly as the type of player who had a nose for the football. In four seasons with Detroit, he tallied 19 interceptions and forced 12 fumbles.

In the 2012 draft, Mayhew opted to select offensive players in the first two rounds. If the Lions general manager is serious about adding play-makers to the defense, he can do so with the team's first two picks in 2013.

With the fifth pick in the first round, the Lions should have the choice of a number of dominant play-making pass rushers such as Damontre Moore, Bjoern Werner, or Jarvis Jones. All three players had at least 12 sacks last season, while Jones forced an NCAA-leading seven fumbles.

In the second round, the Lions could shift the focus to the back end, where a number of top-rated safeties and cornerbacks are likely to be available.