It was announced on August 4th that Charles Clay would be out for "multiple practices," but very little other information has been released about the nature of the injury or the timetable for a potential return.
That changed yesterday, when the Sun-Sentinel's Omar Kelly reported that Clay's injury has been diagnosed as a re-aggravation of his Clay's arthroscopically-repaired knee. It's not uncommon for football players to get their knees "scoped" in the offseason to reduce pain or swelling that comes from wear and tear, and the timetable for return is generally 3-4 weeks after that type of minor operation. What apparently happened to Clay is that he had his knee scoped, then was cleared to return to practice, but during the Dolphins scrimmage on August 2nd, his knee flared up. It's unclear whether the aggravation occurred on a hit or if it was a non-contact injury. Regardless, as of 3 days ago, Charles Clay was still unable to do sprints in practice due to pain and swelling, but he was able to practice catching passes while stationary and wearing a knee brace.
Kelly's report doesn't give a timetable for return. However, the fact that Clay hasn't been asked to undergo a repeat operation so far is good news because it suggests the Dolphins' medical team doesn't consider the injury to be too serious and is satisfied with the healing so far. In other words, it's unlikely that this is a torn knee ligament type of injury situation. Likewise, the Dolphins' tight end signings since the injury to Clay have been "bottom of the roster" type acquisitions, with no rumors of the Dolphins being interested in any trades to address the TE position. That behavior points to Dolphins GM Dennis Hickey not being overly worried about Clay missing too much time.
Head coach Joe Philbin acknowledged the importance of tight end depth in offensive coordinator Bill Lazor's new scheme by admitting the Dolphins could end up keeping up to 5 tight ends on the roster, so I can't imagine the Dolphins would stand pat if they were told Clay's injury was serious, especially since Sims, Hoskins, and Egnew (recently cleared to return to practice from a concussion) have also all been missing time due to injury recently as well.
Given that the nature of the injury was a re-aggravation of a previously operated-on knee, the smart bet is that the Dolphins will be in no rush to bring Clay back during pre-season. Clay hasn't been asked to do any rehab work on his knee just yet. However, a return before the regular season opener on September 7th is definitely possible since Clay will have had a full 5 weeks after the injury to recover at that point.