Why it will happen: Wheaton, the starter opposite Antonio Brown at the X position entering training camp, has the inside track for this job over the 2014 season. He has good deep speed, and despite not being the tallest receiver on the field, Wheaton showed the ability in college and in a few instances his first season in Pittsburgh he can get open deep. A ball-control offense will likely be seen in Pittsburgh this season, and Wheaton won't have a ton of opportunities but he can exploit the heavy reliance on Brown, tight end Heath Miller and running back Le'Veon Bell in the passing game.
An average of three catches a game would be great for Wheaton in his second season, and add in possible special teams contributions, he could find himself the benefactor of a lot of additional snaps - plays he didn't get last season. His 2013 campaign was cut short due to injuries, and while he wouldn't have caught more than 20 passes on the year, he still missed a lot of opportunities after a broken finger in Week 4 held him out of several games.
He's known as a hard worker, and despite not seeing game action, he put the work in during practices last year, giving himself the starting job until someone takes it away.
Why it won't happen: The injury concerns are going to be there, right until they're not. He has to remain healthy, which is the result of both preparation and luck. He hasn't had the luck part to this point.
The Steelers signed veteran free agent Lance Moore this offseason, and drafted Clemson's Martavis Bryant in the fourth round of this draft. Moore could play on the outside in the Steelers' base offensive package, especially considering Miller could shift off the line into the slot for an 11-personnel look should the Steelers want to go into their no-huddle offense from their base package. Moore has more experience and at this point in the careers of both players, could be more versatile.
Bryant, the hope of all "tall receiver" fans, is raw but has impressive talent. The Steelers may simply want to use him early in games to get him involved, eventually rotating the position between the two - or three - receivers. The Steelers' X receiver position appears to be headed for a fluid, dynamic season, one on which multiple players get a relatively equal number of snaps over the second half of the season.
Keys: It will really come down to how well Wheaton knows and understands the offense. Based on a very small sample size of pro plays, his long-term highest and best use may be as a slot receiver, but he's going to be used as the split end right away. If he can show he has both the combination of playbook knowledge as well as the ability to win balls in the air despite a size limitation, He will own the starting position.
It's hard to rule Bryant out as a steadily improving player who rises through the depth chart to take over later in the year, but he has to learn a lot in a relatively short amount of time. It's Wheaton's job to lose right now, and eventually, it'll be Wheaton's job to maintain.