But now Binns is gone for the season after tearing knee ligaments in a one-on-one drill Sunday and reports suggest Matthews is going to be out several weeks with an injury of his own.
So that leaves the Dolphins with Hartline, Wallace, Gibson and ... a whole lot of question marks.
The only one of those seven who has even appeared in an NFL game is McNutt, who was in four games with the Philadelphia Eagles as a rookie in 2012 but didn't catch a pass. He joined the Dolphins in May after being claimed off waivers and has shown early in camp the ability to get open and to make difficult catches.
McNutt, though, isn't very fast and has dropped a few passes.
Of the other six, perhaps Fuller is the most intriguing based on his size and his familiarity with quarterback Ryan Tannehill from their days together at Texas A&M.
That said, the reality is there's no proven commodity on the roster beyond the big three.
Smith was added on Sunday when the team released fourth-string quarterback Aaron Corp, but he figures to be a long shot given no team had picked him until now.
Of the other four, the only one who has made himself noticeable early in camp has been Bumphis, but he also has dropped a few passes, not a luxury he can afford given the fact he's small and not necessarily speedy.
It's uncertain at this point exactly how long Matthews will be out, although reports suggest it's more a matter of weeks than days.
No doubt the Dolphins want to see one of their younger receivers take a big step forward in the next days and weeks, but rest assured they'll also be scouring the waiver wire to see who might become available.
As for veterans still looking for jobs, an interesting name to remember is Greg Camarillo. The former Dolphins starter caught four passes in five games with the New Orleans Saints in 2012.
There are several big-name wide receivers still looking for jobs — Brandon Lloyd, Laurent Robinson, Donald Jones, Randy Moss, Deion Branch, Steve Breaston, Mike Sims-Walker — but it's hard to envision the Dolphins going after one of those guys to fill the role of fourth and/or fifth receivers.
Two more guys still available are former Dolphins players Patrick Turner and Legedu Naanee. Neither is a likely addition, particularly Naanee, who was a big disappointment last season. And, yes, Chad Johnson is still looking for a team, although we don't need to spend much time on him.
Young players still on the market who would make more sense include Brian Robiskie or Tim Toone. One last name to mention is Ruvell Martin, a 6-4, 217 wide receiver who spent his first three NFL seasons (2006-08) with the Green Bay Packers when Joe Philbin was an assistant coach there.