Lions' offense without Calvin Johnson will begin taking shape in workouts

Free agency, the combine and the owners meetings are in the rearview mirror and the draft is just days away. But it’s time to get back to football on the field. Here’s a quick look at the Detroit Lions as they open their offseason workout program Monday:

Biggest challenge facing head coach Jim Caldwell: There are many -- the largest for the regular season will be keeping his job after a rough second season in Detroit. But for now, the biggest challenge will be starting to figure out how to replace Calvin Johnson in the team’s offense. The Lions attempted to do that personnel-wise by signing Marvin Jones from Cincinnati and Jeremy Kerley from the New York Jets. But it’s going to be a group effort between Jones, Kerley, Golden Tate, Eric Ebron and Theo Riddick catching passes from Matthew Stafford. Starting to install an offense that no longer has the benefit of the Calvin Johnson Safety Blanket for Stafford will be the key to spring. It’s going to force Stafford to rely more on his reads and his instincts, which have improved under Caldwell.

Player on the rise: The Lions are likely to need more out of defensive end Devin Taylor in his fourth season. He continued last season to show flashes of being a good NFL starter. He played more snaps in 2015 (522) than he did in his first two seasons combined (504). He finished with 35 tackles and seven sacks, including 4.5 in the second half of the season. He has the prototypical size and arm length. If he can build off what he did at the end of last season in a contract year, he could solve Detroit’s defensive end issues opposite star Ezekiel Ansah.

Player who has the most to prove: Ebron was effective in his second season with the Lions with 47 catches for 537 yards and five touchdowns. With Johnson retired, Ebron has the chance to receive a lot more targets and that could skyrocket his production. He’s one of the biggest mismatches on the Lions and can cause defensive coordinators problems. The issue for him is consistency and his hands. If he can show he can hang on to the ball -- his 10.1 percent drop rate was the worst in the NFL among qualifying pass-catchers last season -- that’ll go a long way to giving Stafford more confidence in him. It’s a big offseason workout period for Ebron.

Surprise player to watch: I was tempted to go with center Gabe Ikard, but considering there is no hitting in the offseason workouts, it’ll be tough to get a gauge on the offensive line until training camp. With that in mind, Alex Carter is going to be a player to pay attention to. He has never played an NFL snap after missing all of last season due to injury, but the 2015 third-round pick has the size and skill set to be a good NFL corner. There’s a wide-open competition opposite Darius Slay, and Carter is the type of tall cornerback Detroit wants. Plus, he’s going to have something to prove after not playing for a year.

Position that should be addressed in the draft: There are many that will be addressed, but the Lions need to upgrade on the offensive line, particularly at tackle. It’s the one obvious need area where Detroit didn’t sign someone who appears like he could be a starter, unless it moves Geoff Schwartz to right tackle. With Riley Reiff entering the final year of his contract and the other options as question marks, the Lions are going to have to address offensive tackle early, perhaps at No. 16. Beyond offensive tackle, Detroit needs defensive ends, a defensive tackle, linebacker, cornerback, safety, wide receiver and a backup quarterback.