Adam Schefter of ESPN reported the Ravens sent the Packers a 2020 seventh-round pick in the deal.
The news comes just two days after Montgomery fumbled during a kickoff return late in the fourth quarter of a 29-27 loss to the Los Angeles Rams rather than take a knee in the end zone.
Michael Silver of NFL.com reported that Montgomery had been instructed by coaches to simply take a knee on the play to ensure Aaron Rodgers had the opportunity to lead a late-game comeback with just over two minutes on the clock.
But one Green Bay player told Silver that Montgomery had thrown a tantrum on the previous offensive series after being taken out of the game and believed Montgomery decided to ignore his coaches' orders out of anger:
"They took him out (the previous drive) for a play and he slammed his helmet and threw a fit. Then (before the kickoff) they told him to take a knee, and he ran it out anyway. You know what that was? That was him saying, 'I'm gonna do me.' It's a f--king joke.
"I mean, what the f--k are you doing? We've got Aaron Rodgers, the best I've ever seen, and you're gonna take that risk? I mean, it's '12'! All you gotta do is give him the ball, and you know what's gonna happen."
A coach told Silver that Rodgers was "very, very mad" after the fumble and "had a right to be."
Montgomery later acknowledged that the return team understood that "if it's in the end zone, keep it in the end zone" but added he didn't directly disregard a coach's orders (h/t Jim Owczarski of PackersNews.com):
"At that point in time, I stood where I always stood, I had a returnable ball. So I made a split-second decision, I don't know if this is going to land on the goal line. So I'm not going to take a knee on the goal line, at the half-yard line and take a chance at putting the game in the ref's hands. Unfortunately, I ended up fumbling the football. I don't think we'd be having this conversation if I didn't fumble the football because we know how good our two-minute offense is.
"But I've never been a guy to completely disobey what I'm being told. I think you can ask a lot of guys in our locker room. That's not what I do. That's not the type of man I am. That's not the kind of person I am."
Montgomery told reporters he also resented that his teammates spoke about the play publicly and made the conversation about his character.
"I'm thoroughly disappointed in the speculation and just the backlash I have to deal with now," he said. "Because now, we're talking about my character. We're not even talking about the fumble anymore, we're talking about my character. We're talking about the reasons why I did what I did, and I'm not OK with that."
On the field, the 25-year-old Montgomery has rushed 26 times for 105 yards and a touchdown, adding 15 receptions for 170 yards. While Aaron Jones and Jamaal Williams have cut into Montgomery's playing time in Green Bay, his versatility as both a runner and receiver have made him a valuable player.
Still, the combination of solid running back depth and any lingering animosity in the locker room toward Montgomery after his fateful fumble made him expendable, and the timing of the move didn't feel coincidental.
As for Baltimore, Montgomery will bring a new dimension to a backfield that also includes Alex Collins and Buck Allen, offering Joe Flacco a solid option in the passing game. But he'll be going from one running back committee to another in a likely role as Baltimore's third-down back.