While all the Detroit Lions' offseason work is important — especially this year with new defensive and offensive systems being installed — training camp is the most crucial time.

Here are five top position battles we’ll be watching:

1. Cornerback: Both starting spots are up for grabs with Chris Houston gone. The most likely candidates are Darius Slay, Rashean Mathis, Cassius Vaughn  and Bill Bentley. Mathis and Vaughn have the most experience, but that doesn’t mean everything. Slay had a good minicamp and Bentley saw plenty of action at nickel in 2013.

2. Right tackle: This is the same battle as in 2013. It was close all the way through a year ago when Corey Hilliard emerged as the starter over the undrafted LaAdrian Waddle. Then Hilliard was injured in the first game so the job was handed to Waddle. Martin Mayhew has said he’s comfortable with either one. Bring it on.

3. Kicker: While the Lions drafted Nate Freese in the seventh round, they also have Giorgio Tavecchio on the roster. Freese consistency at Boston College was amazing. Tavecchio was in camp with the Green Bay Packers last summer and almost won the job over Mason Crosby. The preseason games should determine the winner here.

4. Wide receiver after Calvin Johnson and Golden Tate. The Lions usually keep five wide receivers, we’ll see if Caldwell does it that way. In the mix for the final three spots are Ryan Broyles, Jeremy Ross (who will be the returner), Kris Durham and Kevin Ogletree. Much of this decision could be based on their special teams’ ability too.

5. Defensive end: Ziggy Ansah and Jason Jones should start, but it’s not a given. Jones only played three games last season before he suffered a season-ending knee injury. He’s a versatile veteran who can move inside too.  Ansah improved each game — he’s the best the Lions have at defensive end. Still can’t forget about Devin Taylor who improved as the 2013 season wore on and veteran Darryl Tapp who was signed as a free agent.  Rookie Kyle Van Noy is expected to line up mostly at linebacker, but will be on the defensive end in some packages.

(Training camp opens July 28 with eight of the sessions open to the general public starting on Aug. 1.)

(Follow @PaulaPasche on Twitter. Order her book,  “100 Things Lions Fans Should Know & Do Before They Die’’ here. It’s also available at bookstores.)