IRVING, Texas – The Dallas Cowboys have added defensive linemen Cedric Thornton and Benson Mayowa through free agency. They probably will add a few more pieces to the defense by the end of the month in the draft.

But to Sean Lee, the biggest improvement to the defense has to come from those who have been with the team if the Cowboys want to get back to the playoffs after a miserable 4-12 campaign.

“For us defensively, we have to find a way to step up in big situations. We have to find a way to get more turnovers, make plays in the fourth quarter,” Lee said. “I think they’ve brought in guys who like to play the right way. At the same point, all of us – our main focus is ourselves. How can we get better? How can I play better? How can I play at a higher level so I can make plays? So you look at that and you watch that, but at the end of the day it’s about what type of work we put in, day in and day out, to get better.”

In addition to adding Thornton and Mayowa, the Cowboys retained linebackers Rolando McClain and Kyle Wilber and cornerback Morris Claiborne. They will welcome back their best cornerback, Orlando Scandrick, who missed last season with a knee injury.

The biggest flaw in the Cowboys’ defense last year was takeaways. They forced just 11 and a backup safety, Jeff Heath, led the team in interceptions with two. Starting corners Brandon Carr and Claiborne did not intercept a pass.

In 2014, the Cowboys had 31 takeaways, which was second in the league.

The offensive inefficiency played a part in the inability to take the ball away. The Cowboys rarely held leads and opponents did not have to take as many chances to remain in games. The defense also could not hold leads late.

“It’s just playing better – it’s playing better in all situations,” Lee said. “I’ve said this before: I thought we played well in a lot of situations. The most important situations, though, throughout the entire year, we didn’t play well – fourth quarter, big plays, game-changing plays. We need more of those.”

But how?

“You get better at your craft,” Lee said. “This is the time of year, especially me I’m looking at myself saying, ‘Hey what didn’t I do well last year? Where can I put myself in the position to make more plays?’ Personally I think I can step up and make more big plays and can do that through an entire year. For me I want to be able to put an entire year together and stay healthy and find a way to play at a higher level every game.”