When the Lions ended their offseason program in June, the RB and defensive backfield issues that affected the 2011 season looked to be behind them. RB Jahvid Best participated regularly in drills, Mikel Leshoure’s surgically-repaired ACL looked healthy, and CB Aaron Berry seemed ready to replace the departed Eric Wright.

What a difference six weeks makes.

Two weeks into camp, Berry is gone because of offseason legal issues, and injuries are impacting the roster again. The Lions seem to have gone from a team that looked poised to challenge for a division title, to a team that will have to fight to earn a wild card playoff place.

Questions to be answered in preseason:

Can the backfield contribute to the offense?
If Jahvid Best and Mikel Leshoure don’t return to the lineup before the season begins, the quick answer to this question is probably no. Detroit had the NFC’s 14th ranked run game last season, averaging 95 yards per game on the ground. The fact that Kevin Smith is the only healthy RB with meaningful game experience on the roster doesn’t inspire confidence that the run game will improve in 2012. Leshoure says he’s almost ready to resume practicing with the team, but he’s an unproven commodity. Best hasn’t cleared concussion testing after a nine-month layoff. He simply can’t be counted on to be ready for Week 1. Detroit has some time before it needs to consider bolstering their RB corps, but if the unit’s health doesn’t improve, look for them to add a veteran near the end of camp.

Can the secondary survive in the pass-happy NFC North?
Like the run game, this answer largely depends on DB health. S Louis Delmas’ indefinite absence following knee surgery is a major blow to a secondary that surrendered 90 points -- with an injured and ineffective Delmas -- in its final two 2011 losses. Replacements John Wendling and Amari Spievey, are competent, but their skill doesn’t match what Detroit loses with Delmas out. Rookie CB Bill Bentley has surged ahead in the battle to start opposite Chris Houston, but that’s both a blessing and a curse. If Bentley wins the job over a group of three veteran defenders, it would speak volumes about the strength of the CB corps. Detroit shares a division with Green Bay, who has the conference’s second-best passing offense, and a Chicago team that made significant personnel upgrades to the passing game. If the Lions’ can’t keep opponents off the scoreboard, their potent offense may not be enough to earn them a return trip to the playoffs.

Can the Lions keep their cool?
Lions’ players committed 13 discipline-related personal fouls last season, leading critics to question their ability to remain focused for an entire year. This season’s camp hasn't had any public discipline issues, but the true test of Detroit’s focus will come when they face teams that will try to rattle the Lions’ cage. To contend in 2012, Detroit must focus on beating opponents instead of beating themselves.

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