NFL.com's Jeff Darlington first reported Merling's release, and general manager Jeff Ireland also confirmed the news during an appearance on PFT Live, via the South Florida Sun Sentinel.
A second-round draft pick in 2008, Merling has shown a lack of discipline that has worn thin with the team, sources told Darlington.
"There's a lot of things that go into a decision like this," Ireland told PFT Live. "This has a lot to do with some of the things we learned about him last year and things leading into the offseason. ... We're moving on in a different direction."
The release of Merling is particularly relevant because it is draft week. After losing Kendall Langford in free agency, that's two defensive ends that Miami now must look to replace. Some believe if the Dolphins don't draft a quarterback with the eighth pick, they are likely candidates to push for a defensive end instead. Merling's departure should strengthen those possibilities.
Merling, who just recently signed his tender as a restricted free agent, hadn't attended recent voluntary workouts -- something that also wore down the team and led to the decision to release him.
Follow Jeff Darlington on Twitter @JeffDarlington.