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

Biggest challenge facing head coach Mike Tomlin: Preparing the Steelers' defense for a return to elite status. Despite grumblings about the secondary, the Steelers are closer to becoming a top-shelf defense than many think. The Steelers finished third in the NFL in sacks, fifth in rushing defense and 11th in scoring defense. Tomlin's job will be to unify that group while maximizing the abilities of the secondary, the defensive line and other areas.

Player on the rise: Right tackle Marcus Gilbert. Gilbert played at a Pro Bowl level last season. He edged Von Miller, Khalil Mack, Carlos Dunlap and others during individual matchups. He said his slimmed-down body, playing at just more than 300 pounds, helped his production. He has a chance to sustain that momentum and become a cornerstone for the Steelers' offense by setting the tone this offseason.

Player who has the most to prove: Wide receiver Markus Wheaton. The spotlight rests squarely on Wheaton because of the one-year suspension for Martavis Bryant. Wheaton can win the Steelers' No. 2 receiver job, a role he looked ready for late in 2015. But he failed to catch more than three passes in any of his first 10 games last year. The Steelers need more consistency from Wheaton in a contract year.

Surprise player to watch: Cornerback Doran Grant. The Steelers had basically given up on Grant, who was cut before the regular season and then re-signed after clearing waivers. But Grant, a fourth-round pick, worked behind the scenes, often asking to cover Antonio Brown in practices. In a secondary with two proven starters, Grant should get a few chances to crack the rotation.

Position that should be addressed in draft: Safety. The Steelers feel good about the draft's depth at this position. Expect them to grab a safety somewhere in the first three to four rounds. Corner has been a need for years, but the team's fourth-round pick in 2013, Shamarko Thomas, never took ownership of the safety spot opposite veteran Mike Mitchell. Will Allen likely isn't coming back. That spot couldn't be more vacant. Time for a long-term solution there.