Brandon Gibson is also back from his knee injury (which, unlike Hartline's, required surgery). Some proclaim that Gibson is on the hot seat due to the depth at this position, but Gibson is a savvy route runner in the slot who was developing into one of Tannehill's favorite targets before his injury in Week 7 of last year. Gibson will likely pick up where he left off last season, but his role as slot receiver isn't guaranteed and he will likely be splitting reps.
Rishard Matthews replaced Gibson as the slot receiver last season and retained that role throughout OTAs. Matthews is a physical receiver with strong hands to make spectacular catches. Philbin singled out Matthews, a former seventh round pick, as one of the players who has made a huge leap this offseason. Expect Matthews to be one of the main redzone targets as well (depending on who makes the final 53-man roster).
Jarvis Landry, a second round pick from LSU, has had mixed reviews about his performances in summer workouts (still more good than bad), but the consensus is the same when discussing his future. Everyone I've talked to thinks Landry will be a star for the Dolphins, some going as far to say that Landry will be Tannehill's favorite target by the end of the season.