Polumbus did not transition well to the Broncos' new power blocking scheme, and was replaced on the depth chart by D'Anthony Batiste this pre-season.
Sperry is a second year veteran from Colorado State who played in eight games for the Dolphins last year. He had three catches for 31 yards and a touchdown.
He was originally signed by the San Diego Chargers as an undrafted free agent.
Sperry stands at 6-foot-5, 238 pounds, and is a Colorado native.
Here is his NFL.com scouting report from the 2009 Combine:
A three-time Mountain West Conference honoree, Sperry presents teams with an intriguing blend of size, straight-line speed and soft hands. Few tight ends across the country can match his production, as Sperry leaves the Rams with 141 career receptions for 1,763 yards and 20 touchdowns. Despite his physical tools and eye-popping production, Sperry could struggle acclimating to the NFL. More of an H-back than a traditional tight end capable of blocking out of the three-point stance, Sperry's chances of being anything more than a late-round gamble depends on the trend of NFL offensive coordinators looking for players who present athletic mismatches. Had an arm span of 33 3/8 inches and a hand span of 9 1/2 inches at the combine.