Miami activated Culliver a few weeks ago from the PUP list, so this moves comes as a bit of surprise. He is working his way back from ACL and MCL tears that led to him being placed on injured reserve last November.
Culliver, 27, is a former third-round pick of the 49ers back in 2011. He spent four years in San Francisco before signing a four-year, $32 million contract that included $16 million guaranteed with the Redskins back in March.
Culliver was set to make base salaries of $3 million in 2015 and $8 million from 2016-18 when the Redskins released him this past May. The Dolphins signed him to a contract during the preseason and placed him on the PUP list to open the year.
In 2015, Culliver appeared in six games and recorded 16 tackles and a pass defence for the Redskins. Pro Football Focus had him rated as the No. 110 cornerback out of 111 qualifying players.
Brendel, 24, originally signed on with the Cowboys as an undrafted free agent out of UCLA. He signed a three-year, $1.62 million contract with Dallas before being placed on waivers and joining their practice squad.
The Cowboys eventually placed Brendel on their practice squad injured list and decided to waive him with an injury settlement back in September.
He has yet to appear in an NFL game.
During his college career, Brendel started 52 games for UCLA and was a second-team All-Pac 12 as a senior.