Art Stapleton of The Record noted McAdoo said there was a meeting between Rodgers-Cromartie and himself Tuesday before the defensive back left Wednesday morning.
The 31-year-old Florida native is in the fourth season of a five-year, $35 million contract he signed with the Giants in March 2014. He appeared in each of the team's first five games this season before Wednesday's sudden departure.
"It surprised all of us when we heard what happened," safety Landon Collins said.
Collins also told reporters he believes the decision was a result of an "altercation" Sunday between his secondary mate and McAdoo.
The Giants didn't provide any further information about DRC's decision to exit the facility.
In July, he admitted there was a lot of pressure on the Giants' high-priced defense to perform but said he wasn't letting it impact his preparations, per SiriusXM NFL Radio.
"I never really go in the season with expectations, because I always know there's going to be highs and lows of the season," Rodgers-Cromartie said. "But what I do is just go out there and just prepare and play the best of my ability within the system. The expectation, I know, is just go out there and get it done because a lot has been invested in us. But me, personally, I just want to go out there and just play as hard as I can for as long as I can."
New York is tied with the San Francisco 49ers and Cleveland Browns for the worst record in the NFL at 0-5. It returns to action Sunday night for a nationally broadcast game against the Denver Broncos at Sports Authority Field at Mile High in Colorado.