I'm of the opinion that the answer isn't as cut and dry as to "who," but "whom," will fill the hole left by Bryant; I believe that multiple Steelers will make up for the 50 receptions on 92 targets, 765 receiving yards and 6 touchdowns #10 was responsible for in 2015.
Here are the candidates whom will rise up, and make up for Bryant's absence:
The most obvious choice is the one least talked about in most circles: Antonio Brown.
Many analysts and fans are concerned with discussing which player gets more looks from quarterback Ben Roethlisberger, without facing the elephant in the room; Brown has found a way to catch more balls every year he has been in the league, and has been vocal about wanting to improve on numbers which were close to the best ever.
Brown's 136 catches and 1,834 receiving yards in 2015 were good for the 2nd and 4th best totals all-time. However, his touchdowns took a slide, scoring 3 less times in 2015 than the previous season (10 TDs to 13.)
If anyone could catch more balls, or score more times, to make up for any slack in the Steelers offense, I'd be willing to bet on AB every, single, time.
The second obvious choice is the player labeled as a "Bryant clone" when he was drafted by the Steelers last season.
Thus far, Coates has been turning heads in training camp with spectacular catches… and routine drops as well; something which scouts knocked him for coming out of college.
Coates has some pretty big shoes to fill in his second season, and with few reps, and just as little tape on the 2nd-year receiver, it's uncertain if he'll step right in and take Bryant's place.
The uncertainty of Coates' ability to step right in and start for the 2016 season lead to the Steelers signing Heyward-Bey to a 3-year contract before the start of free agency.
Heyward-Bey admirably stepped in as Bryant's replacement multiple times, including the first five games to start the 2015 season. As a former first round draft pick, with speed and size similar to Bryant, DHB is a threat in the passing game which must be respected. During those first five games, Heyward-Bey caught an average of 3 passes for 42 yards per game. He totaled 17 receptions for 209 yards and 2 scores in those games.
It should be noted that Ben Roethlisberger only played in half of those quarters, getting hurt midway through the 3rd game of the season. DHB saw his role subside as Bryant returned, but found his number called again in the final game of the season, a critical matchup with the playoffs on the line against the Cleveland Browns.
Heyward-Bey caught 2 passes for 74 yards in that game, including a clutch 66 yard bomb by Big Ben.
Ben would also connect with Heyward-Bey on a 58-yard pass in the Denver Broncos Divisional Playoff game.
Similar expectations could be placed on DHB to start this season, easing the pressure on Coates to perform, and perhaps slowly working the younger player into a more prominent role as the year goes by.
The 6-foot-6 prized free agent tight end is recovering from ankle surgery, but hopes to hit the field for Week 1. Described as a "sneaky" pass blocker, many felt Green would be Heath Miller's replacement, but he may end up as more of a fit to pick up both, Miller and Bryant's targets.
A fast, large body who can be seen fulfilling more of a Jimmy Graham style role in Pittsburgh's offense, won't see carries on end-arounds like Bryant, but may be seen streaking down the field, and into the endzone, more times than Miller was.
Still, Miller caught 60 passes last season, 10 more than Bryant and 16 more than our next player… Green will have to have a monster year to be an ideal candidate to replace Martavis, which is why this name is the most likely candidate of those named:
After a slow start in 2015, the former third round pick burst onto the season in the Steelers final six games of the year.
Wheaton started with 49 catches for 273 yards and 1 touchdown, before decimating the Seahawks vaunted defense for 9 receptions, 201 yards and a TD.
Including that game, Wheaton would end 2015's final six games with 28 catches, 476 yards and 4 scores. Wheaton also caught 7 balls in the playoffs, 5 of those in place of Antonio Brown (who missed the game with a concussion.)
Based on his upward trend to end 2015, along with a contract year, all signs point to Wheaton being the "boom or bust" candidate the Steelers need to replace Bryant's production.