The attached picture does not simply show a single player for effect. I have included rather a picture of two plays that exemplify some of the changes undergone in the wide receivers unit.
Though clearly the addition of Mike Wallace grabs the most attention, the Dolphins made another large change to the unit when they signed free agent Brandon Gibson and subsequently shipped Davone Bess to the Cleveland Browns.
The two plays attached may give us a clue as to why the Dolphins did that. Brandon Gibson at 6'0" and 210 lbs is a much larger target than the 5'10" and 190-pound Bess. This is attractive to a head coach Joe Philbin because he likes to send his slot receivers out vertically along the sidelines or up the seam into the middle of the field. Smaller and/or less athletic traditional slot receivers would not necessarily pose as much of a threat on such routes.
In the top part of the picture, you see the 6'3" and 216-pound receiver Marvin McNutt lined up in the slot to the top of the screen. He will run out to the sideline and then vertically to the end zone on a 4th-and-4 against the New Orleans Saints. This was the play on which he scored a 56-yard touchdown.
However, sometimes the switch can backfire. The second play was actually a rare occasion when the Dolphins put Mike Wallace into the slot. The play call was very similar to the one that scored a touchdown against the Saints, but the coverage dictated the routes be modified slightly.
With the safeties in a two-deep zone look, quarterback Ryan Tannehill was tasked with throwing the football to Wallace in between the zones along the sideline, rather than attempting to break through the defense vertically as Pat Devlin later did against the Saints.
In this case against the Buccaneers, Mike Wallace could not execute and finish the catch even though the football was on target. This is a play that a smaller, more execution-savvy player such as Bess would have easily finished.
However, it is important to note that had the defense given a different look, you would have seen Mike Wallace take off up the field vertically with Tannehill attempting to hit him in stride, and a player like Wallace can scarcely be covered in such situations. So, by making changes such as this to the receivers unit and its tendencies, the Dolphins are taking a calculated risk.