Kelly broke up a couple of passes during Sunday's intrasquad scrimmage and provided impressive coverage on rookie wide Chris Chambers.
"Ben has really been one of the real bright spots in camp," Wannstedt said. "If you told me to list five guys that have come in and made a noticeable improvement from a year ago, Ben Kelly would be at the top."
Kelly played in only two games last season before his season was cut short by a knee injury. His action last year was limited to special teams and his work at cornerback was less than impressive.
It's not as if Kelly doesn't have talent. After all, he did earn All-Big 12 first-team accolades in 1999, as both a cornerback and kick returner.
Where Kelly fits in among the Dolphins cornerbacks remains to be seen, but he's certainly making a case for himself. The Dolphins are set in the starting lineup with Patrick Surtain and Sam Madison, and Fletcher figures to be the third corner once he's fully healthy. But nothing is certain beyond that.
"The way Ben is playing, if we had to play a game right now and put Ben in there at the corner and move Patrick inside, I would feel good about that," Wannstedt said. "This week, depending on what Fletcher does, Kelly could see some extensive action with the first group."