This is the third in a three-part series of prove-it players on the Steelers’ offense during organized team activities and minicamp. The Steelers have reliable starters all over the field, so becoming one isn’t as big a part of the criteria as it was for the defensive prove-it players. Instead, let’s examine which players face an especially crucial year in their trajectory.

Player: Markus Wheaton

Steelers receiver Markus Wheaton hopes to build on a 53-catch season in 2014. Evan Habeeb/USA TODAY Sports

Pedigree: A third-round pick in 2013, he finished with 53 catches for 644 yards and two touchdowns in his second season in the Steelers’ offense.

Why he must prove it: Wheaton is the front-runner to become the starting slot receiver, which is desirable in an offense that emphasizes quick passing and yards after the catch. The Steelers need him in that role because many of the team’s receivers are most comfortable outside. Wheaton also is effective on the outside, but he seems a natural for the slot because of his quickness. He’s also 5-foot-11.

Why he really must prove it: Martavis Bryant has been a beast in OTAs. Coming off a 21-yards-per-catch rookie season, Bryant is angling for the No. 2 receiver job behind Antonio Brown. This can help Wheaton assume the slot role, but he also must fight for catches and opportunities. Third-round pick Sammie Coates and veteran Darrius Heyward-Bey will have chances, too, as will tight end Heath Miller.

Why he will prove it: Wheaton has had an impressive OTA, looking poised for growth in the fall. He seems to have rapport with quarterback Ben Roethlisberger, who has been working closely with his young receivers. As Roethlisberger gets comfortable in his fourth year with offensive coordinator Todd Haley, the Steelers will distribute the ball and Wheaton will be involved. Wheaton isn't limited to the slot. His two touchdowns last season came on a go route and a flare out to the sideline.