Underwood, who said he wants to be with his family, has wavered on whether to play in the NFL since being drafted in the first round by the Minnesota Vikings last spring. He played in one preseason game for the Dolphins before attempting suicide, then spent two months in protective care.
"I've got a chance to go home and get some things sorted out," Underwood said before leaving the Dolphins' complex. "Right now I don't think football is the place for me."
The Dolphins announced their decision in a statement from coach Jimmy Johnson.
"He wanted to be with his family in Philadelphia, so we thought it would be in his best interest to release him," Johnson said.
Underwood's departure came one day after another Miami rookie, running back Cecil Collins, was arrested on burglary charges and suspended indefinitely.
Last week, Underwood committed himself to a mental health center in Sunrise, then jumped a fence hours later and fled, police said. A psychiatric nurse at the center told police Underwood had stopped taking medication for manic depression and was possibly suicidal.
On Sept. 26, Underwood was found on a Lansing, Mich. street bleeding from a neck wound. Police said Underwood repeatedly yelled, "I'm not worthy of God" before he used two steak knives to cut his throat at the home of his girlfriend and their 17-month-old twins.
The defensive end was taken with the 29th pick in the April draft by Minnesota and signed a five-year, $5.3 million contract Aug. 1. He walked out of training camp the next day, saying he was torn between a desire to pursue the ministry and the need to support his children.
Underwood sacrificed a $1.75 million signing bonus by leaving the Vikings. But when he was claimed on waivers by Miami, he decided to join the Dolphins.
"You've got all this limelight and glitter flashed before your eyes, and it's hard to pass that up," he said Friday. "I should have stuck with my first decision. It's been a downhill battle ever since. ...
"For a long time I was making bad decisions in my life. It finally caught up with me. You feel like you've got nowhere to turn."
Underwood played in one exhibition game Sept. 2 before hurting a shoulder. After the suicide attempt, he was placed on the reserved-non football injury list, making him ineligible to play the rest of this season.
Underwood said he has been receiving counselig three times a week. He said the only medication he takes is a mild sedative to help him sleep.
His mother, Eileen, complained Friday about the publicity her son has received.
"A lot of that is coming from very unfair coverage," she said from her home in Philadelphia. "People have written that we have been struggling with him and he has had mental illness through the years. He has had no mental illness. I am a little infuriated by that allegation."
She repeated her earlier contention that his problems began when he started attending a controversial church while at Michigan State.
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