Quillen went undrafted out of New Mexico in the 2009 draft and will have a tough time making the roster considering he has to beat out returning starter Lousaka Polite.
Coach Tony Sparano also said after Thursday's practice that rookie offensive tackle SirVincent Rogers had left the team.
Those moves left the Dolphins with 78 players, two under the roster limit.
VETERANS SIT OUT: Linebacker Channing Crowder and nose tackle Jason Ferguson both sat out Thursday morning's practice.
Ferguson was kicked in the chin on Wednesday, while the coaches decided to keep out Crowder, who has had minor knee problems in the past, as a precautionary measure.