What will make a successful camp for Cowboys defense?

 year ago at this time there were dire predictions about the Dallas Cowboys defense. Some wondered if it would be among the worst in NFL history.

They weren't. In fact, the Cowboys finished second in the NFL with 31 takeaways, 19th in the league in yards per game and 15th in points per game. There was no doubt the offense's style of play helped the defense. They simply were not on the field that much because the Cowboys held onto the ball so much.

But the Cowboys knew they needed to get better defensively to be successful in 2015. They added Greg Hardy in free agency. They took Byron Jones and Randy Gregory with their first two picks. The welcome back Sean Lee from injury.

Training camp starts Thursday. What will make for a successful camp for the Cowboys defensively?

Here are three keys:

Keep Sean Lee healthy: Twice in the last week executive vice president Stephen Jones said the No. 1 goal of training camp is to come out as close to 100 percent healthy as possible. The Cowboys know Lee treats practice with the same intensity as a game. They have to make sure Lee paces himself. He missed last year with a torn anterior cruciate ligament. He has not played in a game since Dec. 9, 2013 when he suffered a neck injury. Lee is the Cowboys' best playmaker defensively. The Cowboys have moved him to the weak-side spot where he will be protected somewhat by the defensive tackle, but plays are funneled to the weakside linebacker.

Coming up with a plan: As of today Hardy and Rolando McClain will miss the first four games of the season due to suspension. Hardy's suspension could be reduced if he chooses to take the NFL to court but a decision has yet to be made. Even if Hardy misses two games, he played in only one game last year before he was deactivated and eventually placed on the commissioner's exempt list. While he was able to take part in the offseason program, the Cowboys have to knock off some rust by practicing him more or playing him more than the starters in the preseason games. McClain missed most of the offseason with knee surgery and might not be cleared fully for the start of camp. The balance for McClain might be even more tricky because of his health. If he is right physically and mentally, the Cowboys defense will be infinitely better with McClain and Lee manning two of the three linebacker spots.

Get to the quarterback: The last time we saw the Cowboys play a game, a gimpy Aaron Rodgers was able to light them up. They spent the offseason getting better up front. Rod Marinelli wants to be able to affect the quarterback with only four pass-rushers. He doesn't like to blitz or mix packages often. Hardy, Gregory, DeMarcus Lawrence and Jeremy Mincey give the Cowboys a better quartet of rushers at defensive end than they have had in a few years. Defensive tackle Tyrone Crawford looks primed for a breakout season. Going against the Cowboys offensive line could work two ways for the Cowboys defensive line. If they can't generate much in camp, there is a worry about confidence. But if they can show they can get to the quarterback against a line considered one of the best in the NFL, then that should bolster their confidence heading into the regular season.